WO2017204783A1

WO2017204783A1 - Load aware dynamic random access channel (rach) design

Info

Publication number: WO2017204783A1
Application number: PCT/US2016/033871
Authority: WO
Inventors: Sarabjot SINGH; Ehsan ARYAFAR; Wook Bong Lee; Nageen Himayat; Jing Zhu; Shu-Ping Yeh
Original assignee: Intel Corporation
Priority date: 2016-05-24
Filing date: 2016-05-24
Publication date: 2017-11-30
Also published as: DE112016006899T5

Abstract

An apparatus for use in an eNodeB of a cellular network, that facilitates dynamic random access channel (RACH) design, comprising a processing circuit that, upon execution of instructions from a memory circuit, is configured to determine channel parameters for a RACH phase of a random access channel that exists between the eNodeB and one or more user equipments (UEs) in a coverage area of the eNodeB, based on a load information of the eNodeB. In some embodiments, the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase. Further, the processing circuit is configured to generate a system information message comprising the channel parameters for downlink transmission to the one or more UEs.

Description

LOAD AWARE DYNAMIC RANDOM ACCESS CHANNEL (RACH) DESIGN

FIELD

[0001] The present disclosure relates to cellular networks and, in particular to an apparatus and a method for load aware random access channel (RACH) design that maximizes the utilization of the RACH.

BACKGROUND

[0002] Random access channel (RACH) phase is vital to the design of cellular networks, as it allows user equipments (UEs) to send information to a network before being formally admitted in the network. During the RACH phase, multiple UEs tries to access the network over a shared medium (e.g., random access channel or RACH) between the UEs and the network, using a random access procedure to initiate an uplink (UL) data transfer. The dimensioning of the resources allocated to this random access channel (RACH) phase constitute an important portion of the overhead in the air interface of 5G cellular networks. Provisioning too many resources for the RACH phase leads to lower collisions among UEs, but larger overhead. On the other hand, provisioning too less resources lead to lower overhead but larger collisions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Some examples of circuits, apparatuses and/or methods will be described in the following by way of example only. In this context, reference will be made to the accompanying Figures.

[0004] Fig. 1 a depicts the schematic diagram of a dynamic load aware random access channel (RACH) design comprising a single random access window (RAW), according to one embodiment of the disclosure.

[0005] Fig. 1 b depicts the schematic diagram of a dynamic load aware random access channel (RACH) design comprising multiple random access windows (RAWs), according to one embodiment of the disclosure.

[0006] Fig. 2 depicts an example implementation of a random access procedure in a cellular system that utilizes load aware multi-stage RACH design according to one embodiment of the disclosure. [0007] Fig. 3 depicts an example implementation of a random access procedure in a cellular system that utilizes load aware multi-stage RACH design according to another embodiment of the disclosure.

[0008] Fig. 4 illustrates a block diagram of an apparatus for use in an eNodeB of a cellular network that facilitates dynamic load aware random access channel (RACH) design, according to the various embodiments described herein.

[0009] Fig. 5 illustrates a block diagram of an apparatus for use in a user equipment of a cellular network that facilitates dynamic load aware random access channel (RACH) design, according to the various embodiments described herein.

[0010] Fig. 6 illustrates a flowchart of a method for an eNodeB in a cellular network that facilitates dynamic load aware random access channel (RACH) design, according to one embodiment of the disclosure.

[0011] Fig. 7 illustrates a flowchart of a method for an eNodeB in a cellular network that facilitates dynamic load aware random access channel (RACH) design, according to another embodiment of the disclosure.

[0012] Fig. 8 illustrates a flowchart of a method for a user equipment (UE) in a cellular network that facilitates dynamic load aware random access channel (RACH) design, according to one embodiment of the disclosure.

[0013] Fig. 9 illustrates a flowchart of a method for a user equipment (UE) in a cellular network that facilitates dynamic load aware random access channel (RACH) design, according to another embodiment of the disclosure.

[0014] Fig. 1 0 illustrates, for one embodiment, example components of a User Equipment (UE) device.

DETAILED DESCRIPTION

[0015] In one embodiment of the disclosure, an apparatus for use in an eNodeB of a cellular network, that facilitates dynamic random access channel (RACH) design is disclosed. The apparatus comprises a processing circuit that, upon execution of instructions from a memory circuit, is configured to dynamically determine channel parameters for a RACH phase of a RACH that exists between the eNodeB and one or more user equipments (UEs) in a coverage area of the eNodeB, based on a load information of the eNodeB, wherein the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase; and generate a system information message comprising the channel parameters for downlink transmission to the one or more UEs.

[0016] In one embodiment of the disclosure, an apparatus for use in an eNodeB of a cellular network, that facilitates dynamic random access channel (RACH) design is disclosed. The apparatus comprises a processing circuit that, upon execution of instructions from a memory circuit, is configured to determine a load estimate of a RACH phase of a RACH that exists between the eNodeB and UEs in a coverage area of the eNodeB, comprising information on a number of active user equipments (UEs) in the coverage area of the eNodeB; determine a number of random access windows (RAWs) within the RACH phase, and a number of resources allocated per RAW, based on the determined load estimate; and generate a system information message comprising a broadcast message for downlink transmission to the active UEs, wherein the system information message comprises information on the number of RAWS within the RACH phase and the number of resources allocated per RAW.

[0017] In one embodiment of the disclosure, an apparatus for use in a user equipment (UE) of a cellular network, that facilitates dynamic random access channel (RACH) design is disclosed. The apparatus comprises a processing circuit that, upon execution of instructions from a memory circuit, is configured to receive a system information message from an eNodeB associated therewith comprising channel parameters for a RACH phase of a RACH that exists between the UE and the eNodeB, wherein the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase; generate a random access preamble message for uplink transmission to the eNodeB during a first RAW of the one or more sequential RAWs, upon receiving the system information message; and selectively generate a next random access preamble message during a next RAW of the one or more sequential RAWs within the RACH phase for uplink transmission to the eNodeB, based on an information from the eNodeB. [0018] The present disclosure will now be described with reference to the attached drawing figures, wherein like reference numerals are used to refer to like elements throughout, and wherein the illustrated structures and devices are not necessarily drawn to scale. As utilized herein, terms "component," "system," "interface," "circuit" and the like are intended to refer to a computer-related entity, hardware, software (e.g., in execution), and/or firmware. For example, a component can be a processing circuit (e.g., a microprocessing circuit, a controller, or other processing device), a process running on a processing circuit, a controller, an object, an executable, a program, a storage device, a computer, a tablet PC and/or a user equipment (e.g., mobile phone, etc.) with a processing device. By way of illustration, an application running on a server and the server can also be a component. One or more components can reside within a process, and a component can be localized on one computer and/or distributed between two or more computers. A set of elements or a set of other components can be described herein, in which the term "set" can be interpreted as "one or more."

[0019] Further, these components can execute from various computer readable storage media having various data structures stored thereon such as with a module, for example. The components can communicate via local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network, such as, the Internet, a local area network, a wide area network, or similar network with other systems via the signal).

[0020] As another example, a component can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, in which the electric or electronic circuitry can be operated by a software application or a firmware application executed by one or more processing circuits. The one or more processing circuits can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, a component can be an apparatus that provides specific functionality through electronic components without mechanical parts; the electronic components can include one or more processing circuits therein to execute software and/or firmware that confer(s), at least in part, the functionality of the electronic components. [0021] Use of the word exemplary is intended to present concepts in a concrete fashion. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise, or clear from context, "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied under any of the foregoing instances. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form. Furthermore, to the extent that the terms "including", "includes", "having", "has", "with", or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term

"comprising."

[0022] In the following description, a plurality of details is set forth to provide a more thorough explanation of the embodiments of the present disclosure. However, it will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form rather than in detail in order to avoid obscuring embodiments of the present disclosure. In addition, features of the different embodiments described hereinafter may be combined with each other, unless specifically noted otherwise.

[0023] As indicated above, during the RACH phase multiple UEs try to access the network to initiate uplink (UL) data transfer. At this stage, however, the UEs do not have any resource or channel available to access the network and therefore, a request to attach to the network is transmitted over a shared medium (e.g., RACH) between the UEs and the network, in order to initiate the UL data transfer. During the RACH phase, the UEs access the network using the system resources allocated for the RACH phase. When different UEs contend to attach to the network using the same resources, the utilization of the RACH phase is affected due to collisions. Due to the collisions, only some UEs are successful in attaching to the network during the RACH phase, and the unsuccessful UEs contend to attach to the network during subsequent RACH phases. In some embodiments, this leads to increased latencies for the UEs trying to attach to the network. In some embodiments, the subsequent RACH phases are repeated at periodic intervals. Further, allocating too many resources for a RACH phase leads to increased system overhead. Therefore, the resources of the RACH phase have to be optimally allocated to maximize RACH utilization and minimize system overhead. Some of the conventional approaches utilize static RACH resource allocation, which leads to underutilization in case of low load and overutilization in case of large load. In addition, the static RACH resource allocation leads to higher overhead over the air interface. In some embodiments, the load refers to the number of UEs contending to access the network during a RACH phase.

[0024] Therefore, in order to overcome the disadvantages of the static RACH resource allocation, a new load-aware dynamic RACH design or a load-aware RACH resource allocation is proposed in this disclosure. In particular, this disclosure is directed to a method and an apparatus that facilitates load-aware RACH design during the RACH phase in cellular networks. In one embodiment of the disclosure, a method to dynamically determine a RACH design based on a load information of the network is proposed. In another embodiment, a random access procedure that utilizes the load- aware RACH-design, in order to enable the UEs to attach to the network is proposed. In some embodiments, the proposed load-aware RACH design and the random access procedure improves the utilization of the RACH phase and also provides more flexibility and faster access/lower latencies to UEs intending to attach to the network.

[0025] Fig. 1 a and Fig. 1 b depicts the schematic diagrams of a dynamic load aware random access channel (RACH) design, according to various embodiments described herein. In some embodiments, the proposed RACH design comprises a multi-stage RACH design 150 comprising a plurality of random access windows (RAWs) with a RACH phase (as shown in Fig. 1 b) and in other embodiments, the proposed RACH design comprises a single RAW 100 within the RACH phase (as shown in Fig. 1 a). In some embodiments, the dynamic load aware RACH design comprises dynamically tuning a total allocated resources R of the RACH phase within a single RAW or a plurality of RAWs based on a load information of the network. For example, in the single RAW case, the total allocated resources R within the single RAW is dynamically tuned according to the load information of the RACH phase. Similarly, in the multiple RAW case, the resources for each RAW are dynamically tuned based on the load information of each RAW phase. [0026] In some embodiments, the load information comprises the number of UEs contending to attach to the network (or eNodeB) during a particular RACH/RAW phase. In some embodiments, dynamically allocating the resources of the one or more RAWs within the RACH phase enables to increase the utilization of the RACH phase and also reduces collision probability among different UEs contending to access the network during the RACH phase. In order to dynamically allocate or tune the resources in the single RAW or the multiple RAW case, the load information of the network have to be estimated. In some embodiments, the load information of the network is estimated at the eNodeB utilizing information on a utilization or a collision percentage of a previous RACH phase based on the equation:

Where U is the utilization of a previous RACH phase, L is the average number of UEs (i.e., the load) contending for the network during the RACH phase and R is the total number of RACH resources allocated for the RACH phase. In some embodiments, the utilization corresponds to the number of RACH resources out of the total RACH resources R utilized by the UEs to attach to the network. In some embodiments, the utilization U indicates if the RACH resources are underutilized or over utilized. In some embodiments, the total RACH resources R is predetermined. In some embodiments, it is assumed that the utilization of the previous RACH phase is available at the eNodeB prior to starting a next RACH phase.

[0027] In other embodiments, the load information L of the network is obtained at the eNodeB from another co-existing random access technology (RAT), for example, LTE/4G. For example, in some embodiments, if the decision to associate to 5G RAT is dictated by LTE RAT, then the expected number of UEs (i.e., the load) contending for the RACH is known at the network. Further, in some embodiments, the load information L of the network is determined at the eNodeB by predicting an average traffic in a given area during a particular time and day using machine language and big data techniques.

[0028] Once the load information of a RACH phase is determined, the RACH resources R can be dynamically tuned in order to maximize the utilization of the RACH phase. For example, referring to Fig. 1 a, the dynamic load aware RACH design 1 00 comprises a single RAW 102 having a total allocated resources R to be utilized during the RACH phase 104. Based on the estimated load information L, the resources R of the single RAW 102 can be dynamically tuned in order to maximize the utilization of the RACH phase 104, based on equation (1 ) above. Based on equation (1 ), the utilization U of a RACH phase is maximized when R =L. Therefore, in some embodiments, the resources R of the single RAW 102 is dynamically tuned to be equal to the load L in order to maximize the utilization U of the RACH phase 1 04. In other embodiments, however, metrics other than utilization U can be utilized to tune the resources R of the RAW 102. In some embodiments, the resources R of the RAW 102 are dynamically tuned by the eNodeB based on the estimated load information L. In some

embodiments, the RAW/RACH resources R are defined in terms of time, frequency, preambles or any other orthogonal dimension. For example, the number of resources R for a RACH with T time slots, F frequency bands and P preambles is given by:

R = T x F x P (2)

[0029] In some embodiments, the preambles refer to specific pattern or signature utilized by the UEs to attach to the network during the RACH phase. In some embodiments, the available preambles and the available frequency bands are fixed. In such embodiments, the resources allocated can be dynamically changed by changing the number of time slots. Further, in some embodiments, the resources R for the RACH/RAW 102 can be dynamically tuned based on a performance of the preceding RACH phases. For example, in some embodiments, if the collision probability in the preceding RACH phase was high and the utilization U was low, the resources R for the next RACH phase can be increased. Similarly, if the collision probability in the preceding RACH phase was low and the utilization U was low, the resources R for the next RACH phase can be decreased. In some embodiments, the collision probability of the preceding RACH phase is determined at the eNodeB based on collision statics fed back by the UEs in the coverage area of the eNodeB.

[0030] In some embodiments, based on the estimated load information L of a RACH phase, the RACH phase is divided into a plurality of RAWs as shown in Fig. 1 b. In particular, in this embodiment, the RACH phase 1 52 comprises a first RAW 154, a second RAW 156 and a third RAW 158. However, in other embodiments, the RACH phase 152 can comprise any number RAWs determined based on the load information L of the RACH phase 152. In some embodiments, a total RACH duration of the RACH phase 152 is divided into multiple RAWs with interjected contention resolution periods, for example, the period T1 1 60 between the first RAW 154 and the second RAW 156, and the period T2 162 between the second RAW 154 and the third RAW 158. Further, the first RAW 154 comprises R1 resources, the second RAW 156 comprises R2 resources and the third RAW 158 comprises R3 resources. In some embodiments, the resources R1 , R2 and R3 are also determined based on the load information of the respective RAW.

[0031] In some embodiments, to begin with, all the UEs (i.e., the load L) contend to attach to the network utilizing the resources R1 of the first RAW 154. The UEs that are not successful in attaching to the network during the first RAW 154 contend in the second RAW 156 utilizing the resources R2. Further, the UEs that are not successful in attaching to the network during the second RAW 156 contend in the third RAW 158 utilizing the resources R3. In some embodiments, the information on the UEs that are successful or unsuccessful in attaching to the network during each RAW is provided to the UEs during the contention resolution periods after the respective RAW. In some embodiments, the number of resources R1 , R2 and R3 are predetermined based on a success probability of a respective RAW. For example, in some embodiments, the mean number of successful UEs after the first RAW (i.e., the success probability of the first RAW) is given by:

Where L1 is the mean UE load during the RACH phase.

[0032] Therefore, the mean number of failed UEs after the first RAW is given by:

F{L_ll R₁) = L ₁ = L₁[l -

(4)

After j RAW the mean number of successful UEs is given by:

S{L_s,j-_i, Rj) = ls,j (5)

Similarly, the mean number of unsuccessful UEs after the j^th RAW is given by: (6)

In some embodiments, the mean number of UEs that successfully pass after the RACH phase has to be maximized in order to maximize the utilization of the RACH phase. In some embodiments, the mean number of successful UEs in the RACH phase is given by:

Where N is the total number of RAWs in the RACH phase.

Therefore, the number of RAWs in the RACH phase and the number of resources per RAW can be determined by solving the equation given below:

such that ∑^N _j=1 R_j < R - (N - \)k where R is the total RACH resources, N is the number of RAWs with the RACH phase and k is the overhead due to contention resolution after each RAW.

[0033] Referring back to Fig. 1 b, in one example embodiment, the resources of the first RAW 154 can be determined based on equation (1 ) based on the load information L1 of the RACH phase 152. As indicated above, the utilization U of a RACH/RAW phase is maximum when R = L. Therefore, for the first RAW 154, the resources R1 is tuned to R1 = L1 , where L1 is the mean load of the RACH phase. For the second RAW 156, the load information L2 is determined based on equation (4) or (6) above as

[0034] Once L2 is determined, the resources R2 of the second RAW 156 is tuned to R2 = L2. Similarly, the resources R3 for the third RAW 158 can also be determined. In some embodiments, the above procedure could be utilized for determining the RAW resources for N number of RAWs within a RACH phase. In some embodiments, the information on the number of RAWs within a RACH phase and the number of resources allocated per RAW is determined prior to the RACH phase at the eNodeB and provided to the UEs in the coverage area of the eNodeB. [0035] In some embodiments, the RAW resources R1 , R2 and R3 are different. However, in other embodiments, the RAW resources R1 , R2 and R3 could be kept static and equal, for example, R1 , R2 and R3 equal to R1 . Further, in some

embodiments, the RAW resources R1 , R2 and R3 could be increased or decreased for sequential RAWs, based on the load information of the respective RAW or collision probability of a previous RAW. In some embodiments, in addition to dynamically tuning the RACH resource allocation based on the load information as explained above, the number of random access attempts of the UEs per RAW can also be optimized based on the load information and the resource allocated for that respective RAW. In some embodiments, the number of random access attempts per RAW corresponds to the number of times a UE tries to attach to the network within each RAW. For example, if the load of a particular RAW is low (assuming most of the UE access attempts were successful in the previous RAW) compared to the number of resources allocated for that RAW, then the number of access attempts of the particular RAW can be increased. In some embodiments, the number of access attempts to be utilized in a next RAW is determined at the eNodeB at the end of a preceding RAW and is indicated to the UEs during the contention resolution period.

[0036] Fig. 2 depicts an example implementation of a random access procedure in a cellular system 200 that utilizes load aware multi-stage RACH design according to one embodiment of the disclosure. In some embodiments, the random access procedure corresponds to a procedure by which one or more UEs in a coverage area of an eNodeB tries to attach to the eNodeB (i.e., the network), using one or more RAWs within a RACH phase. In some embodiments, information on the one or more RAWs within the RACH phase are determined at the eNodeB as explained above with respect to Fig. 1 b. The cellular system 200 comprises an eNodeB 202 and a plurality of active UEs (herein after referred to as "UE") that constitute the load of the eNodeB 202. In some embodiments, "active UE" refers to a UE that tries to attach to the eNodeB 202 in order to send uplink (UL) data to the eNodeB 202. In this embodiment, a select UE 204 from the plurality of active UEs in the coverage area of the eNodeB 202 is selected in order to explain the random access procedure associated with the active UEs. The UE 204 initiates the random access procedure, when the UE 204 has UL data to be transmitted to the eNodeB 202. [0037] The eNodeB 202 is configured to determine channel parameters of a RACH phase 203 of a random access channel prior to the RACH phase 203. In some embodiments, the channel parameters comprise information on one or more of a number of sequential random access windows (RAWs) within the RACH phase 203, a number of RAW resources allocated per RAW and a number of access attempts per RAW. In some embodiments, the RACH phase 203 comprises a single RAW and in other embodiments, the RACH phase 203 comprises a plurality of RAWs. In some embodiments, the channel parameters are determined based on a load information of the RACH phase 203, as indicated above with respect to Figs. 1 a and 1 b. Once the channel parameters for the RACH phase 203 are determined, the eNodeB 202 is configured to transmit the channel parameters to one or more UEs in the coverage area of the eNodeB 202 prior to the RACH phase 203, using a system information message 206. In some embodiments, the system information message 206 comprises a broadcast signal. In some embodiments, the eNodeB 202 is configured to determine the channel parameters prior to each RACH phase. However, in other embodiments, the eNodeB 202 is configured to determine the channel parameters only when a load information of the next RACH phase changes from a preceding RACH phase.

[0038] Upon receiving the system information message 206, the UE 204 is configured to generate a random access preamble message 208 for subsequent transmission to the eNodeB 202 using a first RAW 220 of the one or more RAWs (based on the information in the system information message 206) of the RACH phase 203. In some embodiments, the random access preamble message 208 comprises a signature or a specific pattern comprising a "preamble" that enables the eNodeB 202 to differentiate the messages coming from different UEs in the coverage area of the eNodeB 202. The number of preambles available to the UEs is defined by the number of resources allocated for a particular RAW or RACH phase. In some embodiments, the UEs have a predetermined number of preambles available, based on the number of resources allocated for a particular RAW or RACH phase. In some embodiments, more than one UE in the coverage area of the eNodeB 202 utilizes the same preamble in their respective random access preamble message during a particular RAW or RACH phase which leads to collision. In such embodiments, the random access preamble message from some of the UEs experiencing collision would not reach the eNodeB 202. Thus, the UEs experiencing collision would not be successful in attaching to the eNodeB 202. The UEs that do not experience collision are successful in attaching to the network, which in some embodiments, defines a collision criteria. In some embodiments, the random access preamble message 208 comprises a UE identifier RA-RNTI associated with a time slot in which the random access preamble message 208 is transmitted to the eNodeB 202.

[0039] At the end of the first RAW 220, the eNodeB 202 is configured to generate a contention information message 210 for subsequent transmission to the UE 204 during the contention resolution period 222. In some embodiments, the contention information message 210 comprises a broadcast message transmitted to all the UEs in the coverage area of the eNodeB 202. In some embodiments, the contention information message 210 comprises information on the RA-RNTI of the UEs whose random access preamble messages were successfully received during the first RAW 220. If the contention information message 210 comprises the RA-RNTI associated with the UE 204, then it is an indication that the random access preamble message 208 from the UE 204 was successfully received at the eNodeB 202 during the first RAW 220. However, if the contention information message 210 does not comprise the RA-RNTI associated with the UE 204, then it is an indication that the random access preamble message 208 from the UE 204 was not successfully received at the eNodeB 202 during the first RAW 220. In some embodiments, the contention information message 210 further comprises information on a next RAW (e.g., RAW 224) and a random access method (e.g., the number of access attempts per RAW) for the UEs that are not successfully attached to the eNodeB 202 during the first RAW 220.

[0040] In the instances where the contention information message 210 indicates that the random access preamble message 208 from the UE was not successfully received at the eNodeB 202, the UE 204 is configured to contend again to attach to the eNodeB 202 in a next RAW 224 following the contention resolution period 222. In some embodiments, the information contained in the contention information message 210 about the failure of a receipt of the random access preamble message 208 from the UE constitutes a selection criteria. In such embodiments, the UE 204 is configured to generate a next random access preamble message 212 for subsequent transmission to the eNodeB 202 during a next RAW 224 of the RACH phase 203. In some

embodiments, the UE 204 is configured to successively generate random access preamble messages during one or more next sequential RAWs until a respective contention information message indicates a successful receipt of a random access preamble message associated with the UE 204 at the eNodeB 202 or until all the RAWs within the RACH phase 203 are depleted.

[0041] In some embodiments, once the random access preamble message associated with the UE 204, for example, the random access preamble message 208 or 21 2 is successfully received at the eNodeB 202 during any of the one or more sequential RAWs of the RACH phase 203, the UE 204 is configured to receive a random access response message 214 from the eNodeB 202 towards the end of the RACH phase 203. In some embodiments, the random access response message 214 comprises a unicast message addressed to the RA-RNTI of the UE 204 and comprises information on a temporary UE identifier, for example, C-RNTI for the UE 204, a timing advance value for the UE 204 and UL grant resource for the UE 204. In some embodiments, the eNodeB 202 is configured to transmit one or more random access response messages to all the UEs whose random access preamble messages were received during the RACH phase 203. Upon receiving the random access response message 214 from the eNodeB 202, the UE 204 is configured to generate a scheduled transmission message 21 6 comprising a unicast message for subsequent transmission to the eNodeB 202. In some embodiments, the scheduled transmission message 216 comprises a radio resource control (RRC) connection request in order to establish an evolved packet system (EPS) bearer of the UE 204 in the network for UL data transmission.

[0042] Upon the successful receipt of the scheduled transmission message 216 and the establishment of an RRC connection with the UE 204, the eNodeB 202 is configured to generate a contention resolution message 218 comprising a unicast message for subsequent transmission to the UE 204. In some embodiments, the contention resolution message 218 comprises an RRC connection setup message indicating the successful establishment of the RRC connection of the UE 204 with the eNodeB 202. In some embodiments, when the random access preamble message (for example, 208 or 21 2) from the UE 204 is not successfully received at the eNodeB 202 during the one or more sequential RAWs of the RACH phase 203, the UE 204 is configured to contend again to attach to the eNodeB 202 during a next RACH phase following the RACH phase 203. In some embodiments, the RACH phases associated with the random access channel that exists between the eNodeB 202 and the UEs in the coverage area of the eNodeB 202 are repeated at predetermined time intervals.

[0043] Fig. 3 depicts an example implementation of a random access procedure in a cellular system 300 that utilizes load aware multi-stage RACH design according to another embodiment of the disclosure. The cellular system 300 in Fig. 3 is similar to the cellular system 200 in Fig. 2, comprising an eNodeB 302 and a plurality of active UEs (herein after referred to as "UE") that constitute the load of the eNodeB 302. In this embodiment, a select UE 304 from the plurality of active UEs in the coverage area of the eNodeB 302 is selected in order to explain the random access procedure associated with the active UEs. The UE 304 initiates the random access procedure, when the UE 304 has UL data to be transmitted to the eNodeB 302. As indicated above with respect to Fig. 2, the eNodeB 302 in Fig. 3 is configured to determine channel parameters of a RACH phase 303 of a random access channel prior to the RACH phase 303. In some embodiments, the channel parameters comprise information on one or more of a number of sequential random access windows (RAWs) within the RACH phase 303, a number of RAW resources allocated per RAW and a number of access attempts per RAW.

[0044] In some embodiments, the RACH phase 303 comprises a single RAW and in other embodiments, the RACH phase 303 comprises a plurality of RAWs. In some embodiments, the channel parameters are determined based on a load information of the RACH phase 303, as indicated above with respect to Figs. 1 a and 1 b. Once the channel parameters for the RACH phase 303 are determined, the eNodeB 302 is configured to transmit the channel parameters to the one or more UEs (e.g., the UE 304) in the coverage area of the eNodeB 302 prior to the RACH phase 303, using a system information message 306. In some embodiments, the system information message 306 comprises a broadcast signal. In some embodiments, the eNodeB 302 is configured to determine the channel parameters prior to each RACH phase. However, in other embodiments, the eNodeB 302 is configured to determine the channel parameters only when a load information of the next RACH phase changes from a preceding RACH phase. [0045] Upon receiving the system information message 306, the UE 304 is configured to generate a random access preamble message 308 for subsequent transmission to the eNodeB 302 using a first RAW 320 of the one or more RAWs (based on the information in the system information message 306) of the RACH phase 303. In some embodiments, the random access preamble message 308 comprises a signature or a specific pattern comprising a "preamble" that enables the eNodeB 302 to differentiate the messages coming from different UEs in the coverage area of the eNodeB 302. In some embodiments, more than one UE in the coverage area of the eNodeB 302 utilizes the same preamble in their respective random access preamble message during a particular RAW or RACH phase which leads to collision, as indicated above with respect to Fig. 2. In such embodiments, the random access preamble message from some of the active UEs experiencing collision would not reach the eNodeB 302. Thus, the UEs experiencing collision would not be successful in attaching to the eNodeB 302. The UEs that do not experience collision are successful in attaching to the network, which in some embodiments, defines a collision criteria. In some embodiments, the random access preamble message 308 comprises a UE identifier RA-RNTI associated with a time slot in which the random access preamble message 308 is transmitted.

[0046] In the embodiments where the random access preamble message 308 is successfully received at the eNodeB 302 during the first RAW 320, the eNodeB 302 is configured to generate a random access response message 310 for subsequent transmission to the UE 304 during a contention resolution period 322 following the first RAW 320. In some embodiments, the random access response message 310 comprises a unicast message addressed to the RA-RNTI of the UE 304 and comprises information on a temporary UE identifier, for example, C-RNTI for the UE 304, a timing advance value for the UE 304 and UL grant resource for the UE 304. Upon receiving the random access response message 310 from the eNodeB 302, the UE 304 is configured to generate a scheduled transmission message 31 2 comprising a unicast message for subsequent transmission to the eNodeB 302 during the contention resolution period 322. In some embodiments, the scheduled transmission message 31 2 comprises a radio resource control (RRC) connection request in order to establish an evolved packet system (EPS) bearer of the UE 304 in the network for UL data transmission. [0047] Upon the successful receipt of the scheduled transmission message 312 and the establishment of an RRC connection with the UE 304, the eNodeB 302 is configured to generate a contention resolution message 314 comprising a unicast message for subsequent transmission to the UE 304 during the contention resolution period 322. In some embodiments, the contention resolution message 314 comprises an RRC connection setup message indicating the successful establishment of the RRC connection of the UE 304 with the eNodeB 302. In some embodiments, when the random access preamble message 308 from the UE 304 is not successfully received at the eNodeB 302 during the first RAW 320 of the RACH phase 303, the UE 304 does not receive the contention resolution message 314 during the contention resolution period 322, in response to transmitting the random access preamble message 308 during the first RAW 320. In some embodiments, the failure of the receipt of the contention resolution message 314 from the eNodeB 302 during the contention resolution period 322 constitutes a selection criteria. In such embodiments, the UE 304 is configured to contend again to attach to the eNodeB 302 during a next RAW 324 of the RACH phase 303. In such instances, the UE 304 is configured to generate a next random access preamble message 316 at the end of the contention resolution period 322 for subsequent transmission to the eNodeB 302 during the next RAW 324. In some embodiments, the RACH phase 303 comprises a plurality of RAWs with interjected contention resolution periods and the UE 304 is configured to successively generate one or more next random access preamble messages until the UE 304 is successfully attached to the network (i.e., a random access preamble message associated with the UE 304 is successfully received at the eNodeB 302) or until the one or more sequential RAWs within the RACH phase 303 are depleted.

[0048] In some embodiments, the random access procedures described above with respect to Figs. 2 and 3 can also be applied in the sector sweep procedures of 5G/IEEE 802.1 1 ay or WiGiG systems, by accounting for the expected number of sector sweep by UEs into the network load and tuning the corresponding random access resources as outlined before. In such embodiments, the RACH opportunities or optimal access attempts may be notified through either directional unicast messages to UEs that passed contention (if direction information is available at eNodeB) or through another RAT like LTE or IEEE 802.1 1 ac/n/b/g. [0049] Fig. 4 illustrates a block diagram of an apparatus 400 for use in an eNodeB of a cellular network that facilitates dynamic random access channel (RACH) design, according to the various embodiments described herein. The eNodeB is described herein with reference to the eNodeB 202 in Fig. 2 for the random access procedure in the cellular system 200 in Fig. 2 and with reference to the eNodeB 302 in Fig. 3 for the random access procedure in the cellular system 300 in Fig. 3. The apparatus 400 includes a receiver circuit 420, a processing circuit 430, and a transmitter circuit 410. Further, in some embodiments, the apparatus 400 comprises a memory circuit 440 coupled to the processing circuit 430. Each of the receiver circuit 420 and the transmitter circuit 41 0 are configured to be coupled to one or more antennas, which can be the same or different antenna(s). Further, in some embodiments, the apparatus comprises a memory circuit 440 coupled to the processing circuit 430. In some embodiments, the receiver circuit 420 and the transmitter circuit 410 can have one or more components in common, and both can be included within a transceiver circuit, while in other aspects they are not. In various embodiments, the apparatus 400 can be included within an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (Evolved NodeB, eNodeB, or eNB).

[0050] For the random access procedure in the cellular system 200 in Fig. 2, the apparatus 400 could be included within the eNodeB 202 in Fig. 2. The processing circuit 430 is configured to determine channel parameters for a RACH phase (e.g., the RACH phase 203) of a random access channel that exists between the eNodeB (e.g., the eNodeB 202) and one or more user equipments (UEs) (e.g., the UE 204) in a coverage area of the eNodeB, based on a load information of the eNodeB. In some embodiments, the channel parameters comprise information on one or more of a number of sequential random access windows (RAWs) within the RACH phase (e.g., the RACH phase 203), a number of RAW resources allocated per RAW and a number of access attempts per RAW. In some embodiments, the channel parameters are determined based on the load information of the RACH phase, as indicated above with respect to Figs. 1 a and 1 b and are stored in the memory circuit 440. Upon determining the channel parameters, the processing circuit 430 is configured to generate a system information message (e.g., the system information message 206) comprising a broadcast message for subsequent transmission to the one or more user equipments (UEs) (e.g., the UE 204) in the coverage area of the eNodeB via a transmit circuit 410, prior to the RACH phase (e.g., the RACH phase 203). In some embodiments, the system information message comprises the determined channel parameters of the RACH phase.

[0051] The processing circuit 430 is further configured to selectively receive a random access preamble message (e.g., the random access preamble message 208) from a select UE (e.g., UE 204) in the coverage area of the eNodeB during a first RAW (e.g., the first RAW 220) of the RACH phase, via a receive circuit 420, in response to transmitting the system information message. In other embodiments, processing circuit 430 is configured to selectively receive one or more random access preamble messages associated with the one or more UEs in the coverage area of the eNodeB. In some embodiments, the processing circuit 430 is further configured to generate a contention information message (e.g., the contention information message 210) comprising a broadcast message during a contention resolution period (e.g., the contention resolution period 222) following the first RAW. In some embodiments, the contention information message is subsequently transmitted to the one or more UEs (e.g., the UE 204) in the coverage area of the eNodeB via the transmit circuit 41 0. In some embodiments, the contention resolution message indicates a status of the receipt of the random access preamble message at the eNodeB during the first RAW.

[0052] In some embodiments, the processing circuit 430 is further configured to generate a random access response message (e.g., the random access response message 214) comprising a unicast message at the end of the RACH phase, in response to receiving the random access preamble message (e.g., the random access preamble message 204) from the select UE during the first RAW (e.g., the first RAW 220). In some embodiments, the processing circuit 430 is further configured to provide the generated random access response message to the transmit circuit 410 for subsequent transmission to the select UE. In some embodiments, the processing circuit 430 is further configured to receive a scheduled transmission message (e.g., the scheduled transmission message 21 6) comprising a unicast message via the receive circuit 420 from the select UE, in response to transmitting the random access response message to the select UE. In some embodiments, the processing circuit 430 is further configured to generate contention resolution message (e.g., the contention resolution message 218) for subsequent transmission to the select UE (e.g., the UE 204) via the transmit circuit 410, in response to receiving the scheduled transmission message.

[0053] In some embodiments, if the random access preamble message (e.g., the random access preamble message 208) from the select UE is not successfully received at the eNodeB during the first RAW, the processing circuit 430 is configured to selectively receive a next random access preamble message (e.g., the random access preamble message 212) from the select UE during a next RAW (e.g., the next RAW 224) of the one or more sequential RAWs of the RACH phase.

[0054] For the random access procedure in the cellular system 300 in Fig. 3, the apparatus 400 could be included within the eNodeB 302 in Fig. 3. The processing circuit 430 is configured to determine channel parameters for a RACH phase (e.g., the RACH phase 303) of a RACH that exists between the eNodeB (e.g., the eNodeB 302) and one or more user equipments (UEs) (e.g., the UE 304) in a coverage area of the eNodeB, based on a load information of the eNodeB. In some embodiments, the channel parameters comprise information on one or more of a number of sequential random access windows (RAWs) within the RACH phase (e.g., the RACH phase 303), a number of RAW resources allocated per RAW and a number of access attempts per RAW. In some embodiments, the channel parameters are determined based on the load information of the RACH phase 303, as indicated above with respect to Figs. 1 a and 1 b and are stored in the memory circuit 440. Upon determining the channel parameters, the processing circuit 430 is configured to generate a system information message (e.g., the system information message 306) comprising a broadcast message for subsequent transmission to the one or more user equipments (UEs) (e.g., the UE 304) in the coverage area of the eNodeB via a transmit circuit 410, prior to the RACH phase (e.g., the RACH phase 303). In some embodiments, the system information message comprises the determined channel parameters of the RACH phase.

[0055] The processing circuit 430 is further configured to selectively receive a random access preamble message (e.g., the random access preamble message 308) from a select UE (e.g., UE 304) in the coverage area of the eNodeB during a first RAW (e.g., the first RAW 320) of the RACH phase, via a receive circuit 420, in response to transmitting the system information message. In some embodiments, the processing circuit 430 is further configured to selectively generate a random access response message (e.g., the random access response message 310) comprising a unicast message, in response to receiving the random access preamble message (e.g., the random access preamble message 308) from the select UE during the first RAW (e.g., the first RAW 320). In some embodiments, the processing circuit 430 is further configured to provide the generated random access response message to the transmit circuit 41 0 for subsequent transmission to the select UE. In some embodiments, the processing circuit 430 is further configured to receive a scheduled transmission message (e.g., the scheduled transmission message 312) comprising a unicast message via the receive circuit 420 from the select UE, in response to transmitting the random access response message to the select UE. In some embodiments, the processing circuit 430 is further configured to generate contention resolution message (e.g., the contention resolution message 314) for subsequent transmission to the select UE (e.g., the UE 304) via the transmit circuit 410, in response to receiving the scheduled transmission message.

[0056] In some embodiments, if the random access preamble message (e.g., the random access preamble message 308 from the select UE (e.g., the UE 304) is not received at the processing circuit 430 during the first RAW (i.e., the first RAW 320), the processing circuit 430 is configured to selectively receive a next random access preamble message (e.g., the random access preamble message 316) from the select UE during a next RAW (e.g., the next RAW 324) of the one or more sequential RAWs of the RACH phase (e.g., the RACH phase 303). In some embodiments, the processing circuit 430 is configured to receive the next random access preamble message via the receive circuit 420. In some embodiments, the processing circuit 430 is configured to receive one or more next random access preamble messages successively from the select UE (e.g., the UE 304) using one or more next RAWs until the random access preamble message associated with the select UE is received at the eNodeB or until the one or more sequential RAWs are depleted.

[0057] Fig. 5 illustrates a block diagram of an apparatus 500 for use in a user equipment (UE) of a cellular network that facilitates dynamic random access channel (RACH) design, according to the various embodiments described herein. The UE is described herein with reference to the UE 204 in Fig. 2 for the random access procedure in the cellular system 200 in Fig. 2 and with reference to the UE 304 in Fig. 3 for the random access procedure in the cellular system 300 in Fig. 3. The apparatus 500 includes a receiver circuit 510, a processing circuit 530, and a transmitter circuit 520. Further, in some embodiments, the apparatus 500 comprises a memory circuit 540 coupled to the processing circuit 530. Each of the receiver circuit 510 and the transmitter circuit 520 are configured to be coupled to one or more antennas, which can be the same or different antenna(s). In some embodiments, the receiver circuit 510 and transmitter circuit 520 can have one or more components in common, and both can be included within a transceiver circuit, while in other aspects they are not. In various embodiments, the apparatus 500 can be included within a UE, for example, with apparatus 500 (or portions thereof) within a receiver and transmitter or a transceiver circuit of a UE.

[0058] For the random access procedure in the cellular system 200 in Fig. 2, the apparatus 500 could be included within the UE 204 in Fig. 2. The processing circuit 530 is configured to receive a system information message (e.g., the system information message 206 from an eNodeB (e.g., the eNodeB 202), comprising channel parameters for a RACH phase (e.g., the RACH phase 203) of a RACH that exists between the UE and the eNodeB. In some embodiments, the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase and the received channel parameters are stored in the memory circuit 540. Upon receiving the system information message, the processing circuit 530 is configured to generate a random access preamble message (e.g., the random access preamble message 208) for subsequent transmission to the eNodeB (e.g., the eNodeB 202) via the transmit circuit 520 during a first RAW (e.g., the first RAW 220) of the one or more sequential RAWs.

[0059] In some embodiments, the random access preamble message is generated at the processing circuit 530 in order to establish an attachment of the UE 204 to the eNodeB. The processing circuit 530 is further configured to receive a contention information message (e.g., the contention information message 210) from the eNodeB via the receive circuit 510, during a contention resolution period (e.g., the contention resolution period 222) following the first RAW. In some embodiments, the contention information message comprises information on a status of the receipt of the random access preamble message at the eNodeB during the preceding RAW (e.g., the first RAW 220).

[0060] In some embodiments, if the contention information message indicates that the random access preamble message (e.g., the random access preamble message 208) was not successfully received during the first RAW, the processing circuit 530 is configured to generate a next random access preamble message (e.g., the next random access preamble message 212) for subsequent transmission to the eNodeB during a next RAW (e.g., the next RAW 224) of the one or more sequential RAWs within the RACH phase. In some embodiments, the processing circuit 530 is configured to successively generate one or more next random access preamble messages during the one or more next RAWs until a respective contention information message indicates a successful receipt of the respective random access preamble message at the eNodeB or until the one or more next RAWs of the RACH phase are depleted.

[0061] On the other hand, if the contention information message indicates that the random access preamble message (e.g., the random access preamble message 208) was successfully received during the first RAW (e.g., the first RAW 220), the processing circuit 530 is configured to receive a random access response message (e.g., the random access response message 214) from the eNodeB via the receive circuit 510, at the end of the RACH phase. In some embodiments, the processing circuit 530 is further configured to generate a scheduled transmission message (e.g., the scheduled transmission message 21 6) for subsequent transmission to the eNodeB vai the transmit circuit 520, in response to receiving the random access response message. Further, the processing circuit 530 is configured to receive a contention resolution message (e.g., the contention resolution message218) from the eNodeB via the receive circuit 51 0, in response to transmitting the scheduled transmission message. In some embodiments, the contention resolution message from the eNodeB indicates the successful establishment of an RRC connection of the UE 204 in the network.

[0062] For the random access procedure in the cellular system 300 in Fig. 3, the apparatus 500 could be included within the UE 304 in Fig. 3. The processing circuit 530 is configured to receive a system information message (e.g., the system information message 306 from an eNodeB (e.g., the eNodeB 302), comprising channel parameters for a RACH phase (e.g., the RACH phase 303) of a RACH that exists between the UE and the eNodeB. In some embodiments, the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase and the channel parameters received at the processing circuit 530 are stored in the memory circuit 540. Upon receiving the system information message, the processing circuit 530 is configured to generate a random access preamble message (e.g., the random access preamble message 308) for subsequent transmission to the eNodeB (e.g., the eNodeB 302) via the transmit circuit 520 during a first RAW (e.g., the first RAW 320) of the one or more sequential RAWs. In some embodiments, the random access preamble message is generated at the processing circuit 530 in order to establish an attachment of the UE 304 to the eNodeB.

[0063] In some embodiments, if the random access preamble message (e.g., the random access preamble message 308) was successfully received at the eNodeB, the processing circuit 530 is configured to receive a random access response message (e.g., the random access response message 31 0) from the eNodeB via the receive circuit 51 0, during a contention resolution period (e.g., the contention resolution period 322) following the first RAW. In some embodiments, the processing circuit 530 is further configured to generate a scheduled transmission message (e.g., the scheduled transmission message 31 2) during the contention resolution period for subsequent transmission to the eNodeB via the transmit circuit 520, in response to receiving the random access response message. Further, the processing circuit 530 is configured to receive a contention resolution message (e.g., the contention resolution message 314) from the eNodeB via the receive circuit 510, in response to transmitting the scheduled transmission message. In some embodiments, the contention resolution message from the eNodeB indicates the successful attachment of the UE 304 to the eNodeB 302.

[0064] On the other hand, if the random access preamble message (e.g., the random access preamble message 308) was not successfully received at the eNodeB during the first RAW, the processing circuit 530 does not receive the contention resolution message (e.g., the contention resolution message 314) during the contention resolution period (e.g., the contention resolution period 322) following the first RAW. In such instances, the processing circuit 530 is configured to generate a next random access preamble message (e.g., the next random access preamble message 316) for subsequent transmission to the eNodeB during a next RAW (e.g., the next RAW 324) of the one or more sequential RAWs within the RACH phase. In some embodiments, the processing circuit 530 is configured to successively generate one or more next random access preamble messages during the one or more next RAWs until a contention resolution message is received at the processing circuit 530, in response to transmitting the next random access preamble message or until the one or more next RAWs of the RACH phase are depleted.

[0065] Fig. 6 illustrates a flowchart of a method 600 for an eNodeB of a cellular network that facilitates dynamic random access channel (RACH) design, according to one embodiment of the disclosure. The method 600 is described herein with reference to the apparatus 400 in Fig. 4 and the cellular system 200 in Fig. 2. In some

embodiments, the apparatus 400 is included within the eNodeB 202 of the cellular system 200 in Fig. 2. At 602, channel parameters for a RACH phase of a RACH that exists between the eNodeB and one or more user equipments (UEs) in a coverage area of the eNodeB are determined at the processing circuit 430, based on a load

information of the eNodeB and stored in the memory circuit 440. In some

embodiments, the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase. At 604, a system information message comprising the determined channel parameters is generated at the processing circuit 430 and transmitted to the one or more UEs in the coverage area of the eNodeB via the transmit circuit 410.

[0066] At 606, a random access preamble message is selectively received at the processing circuit 430 from a select UE of the one or more UEs, via the receive circuit 420 during a first RAW of the one or more sequential RAWs, in response to transmitting the system information message. At 608, a contention information message is generated at the processing circuit 430 and transmitted to the select UE via the transmit circuit 41 0 during a contention resolution period following the first RAW phase. In some embodiments, the contention resolution message comprises information on a status of the receipt of the random access preamble message at the eNodeB during the first RAW. At 610, a next random access preamble message is selectively received at the processing circuit 430 from the select UE, via the receive circuit 420 during a next RAW of the one or more sequential RAWs, in response to transmitting the contention information message. [0067] Fig. 7 illustrates a flowchart of a method 700 for an eNodeB of a cellular network that facilitates dynamic random access channel (RACH) design, according to one embodiment of the disclosure. The method 700 is described herein with reference to the apparatus 400 in Fig. 4 and the cellular system 300 in Fig. 3. In some

embodiments, the apparatus 400 is included within the eNodeB 302 of the cellular system 300 in Fig. 3. At 702, channel parameters for a RACH phase of a RACH that exists between the eNodeB and one or more user equipments (UEs) in a coverage area of the eNodeB are determined at the processing circuit 430, based on a load

information of the eNodeB. In some embodiments, the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase. At 704, a system information message comprising the determined channel parameters is generated at the processing circuit 430 and transmitted to the one or more UEs in the coverage area of the eNodeB via the transmit circuit 410.

[0068] At 706, a random access preamble message is selectively received at the processing circuit 430 from a select UE of the one or more UEs, via the receive circuit 420 during a first RAW of the one or more sequential RAWs, in response to transmitting the system information message. At 708, a contention resolution message is selectively generated at the processing circuit 430 and transmitted to the select UE via the transmit circuit 41 0 during a contention resolution period following the first RAW, when the random access preamble message from the select UE is successfully received at the processing circuit 430 during the first RAW. At 710, a next random access preamble message is selectively received at the processing circuit 430 from the select UE, via the receive circuit 420 during a next RAW of the one or more sequential RAWs, when the random access preamble message from the select UE is not successfully received at the processing circuit 430 during the first RAW.

[0069] Fig. 8 illustrates a flowchart of a method 800 for a user equipment (UE) of a cellular network that facilitates dynamic random access channel (RACH) design, according to one embodiment of the disclosure. The method 800 is described herein with reference to the apparatus 500 in Fig. 5 and the cellular system 200 in Fig. 2. In some embodiments, the apparatus 500 is included within the UE 204 of the cellular system 200 in Fig. 2. At 802, a system information message comprising channel parameters for a RACH phase is received at the processing circuit 530 from the eNodeB via the receive circuit 510. At 804, a random access preamble message is generated at the processing circuit 530 and transmitted to the eNodeB via the transmit circuit 520 during a first RAW of the one or more sequential RAWs of the RACH phase, in response to receiving the system information message.

[0070] At 806, a contention information message is received at the processing circuit 530 from the eNodeB via the receive circuit 510, during a contention resolution period following the first RAW. In some embodiments, the contention information message indicates a status of the receipt of the random access preamble message at the eNodeB. At 808, a next random access preamble message is selectively generated at the processing circuit 530 and transmitted to the eNodeB via the transmit circuit 520 during a next RAW of the one or more sequential RAWs, based on the information contained in the contention information message. In some embodiments, the next random access preamble message is selectively generated when the contention information message indicates that the random access preamble message was not successfully received at the eNodeB during the first RAW.

[0071] Fig. 9 illustrates a flowchart of a method 900 for a user equipment (UE) of a cellular network that facilitates dynamic random access channel (RACH) design, according to one embodiment of the disclosure. The method 900 is described herein with reference to the apparatus 500 in Fig. 5 and the cellular system 300 in Fig. 3. In some embodiments, the apparatus 500 is included within the UE 304 of the cellular system 300 in Fig. 3. At 902, a system information message comprising channel parameters for a RACH phase is received at the processing circuit 530 from the eNodeB via the receive circuit 510. At 904, a random access preamble message is generated at the processing circuit 530 and transmitted to the eNodeB via the transmit circuit 520 during a first RAW of the one or more sequential RAWs of the RACH phase, in response to receiving the system information message.

[0072] At 906, a contention resolution message is selectively received at the processing circuit 530 from the eNodeB via the receive circuit 510, during a contention resolution period following the first RAW. In some embodiments, the contention resolution message indicates a receipt of the random access preamble message at the eNodeB. At 908, a next random access preamble message is selectively generated at the processing circuit 530 and transmitted to the eNodeB via the transmit circuit 520 during a next RAW of the one or more sequential RAWs following the contention resolution period, when the contention resolution message from the eNodeB is not received at the processing circuit 530 during the contention resolution period.

[0073] While the methods are illustrated and described above as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the disclosure herein. Also, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

[0074] Embodiments described herein may be implemented into a system using any suitably configured hardware and/or software. Fig. 10 illustrates, for one embodiment, example components of a User Equipment (UE) device 1000. In some embodiments, the UE device 1000 may include application circuitry 1002, baseband circuitry 1 004, Radio Frequency (RF) circuitry 1006, front-end module (FEM) circuitry 1008 and one or more antennas 1010, coupled together at least as shown.

[0075] The application circuitry 1002 may include one or more application processing circuits. For example, the application circuitry 1002 may include circuitry such as, but not limited to, one or more single-core or multi-core processing circuits. The processing circuit(s) may include any combination of general-purpose processing circuits and dedicated processing circuits (e.g., graphics processing circuits,

application processing circuits, etc.). The processing circuits may be coupled with and/or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the system.

[0076] The baseband circuitry 1004 may include circuitry such as, but not limited to, one or more single-core or multi-core processing circuits. The baseband circuitry 1004 may include one or more baseband processing circuits and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 1006 and to generate baseband signals for a transmit signal path of the RF circuitry 1006. Baseband processing circuity 1004 may interface with the application circuitry 1002 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 1006. For example, in some embodiments, the baseband circuitry 1004 may include a second generation (2G) baseband processing circuit 1004a, third generation (3G) baseband processing circuit 1004b, fourth generation (4G) baseband processing circuit 1004c, and/or other baseband processing circuit(s) 1004d for other existing

generations, generations in development or to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 1004 (e.g., one or more of baseband processing circuits 1004a-d) may handle various radio control functions that

enable communication with one or more radio networks via the RF circuitry 1006. The radio control functions may include, but are not limited to, signal

modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 1 004 may include Fast-Fourier Transform (FFT), precoding, and/or constellation

mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 1004 may include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality.

Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

[0077] In some embodiments, the baseband circuitry 1004 may include elements of a protocol stack such as, for example, elements of an evolved universal terrestrial radio access network (EUTRAN) protocol including, for example, physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or radio resource control (RRC) elements. A central processing unit (CPU) 1004e of the baseband circuitry 1004 may be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRC layers. In some embodiments, the baseband circuitry may include one or more audio digital signal processing circuit(s) (DSP) 1004f. The audio DSP(s) 1004f may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 1004 and the application circuitry 1002 may be implemented together such as, for example, on a system on a chip (SOC).

[0078] In some embodiments, the baseband circuitry 1004 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 1004 may support communication with an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 1004 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

[0079] RF circuitry 1006 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 1006 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 1006 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 1008 and provide baseband signals to the baseband circuitry 1004. RF circuitry 1006 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 1004 and provide RF output signals to the FEM circuitry 1008 for transmission.

[0080] In some embodiments, the RF circuitry 1006 may include a receive signal path and a transmit signal path. The receive signal path of the RF circuitry 1006 may include mixer circuitry 1 006a, amplifier circuitry 1006b and filter circuitry 1006c. The transmit signal path of the RF circuitry 1006 may include filter circuitry 1006c and mixer circuitry 1006a. RF circuitry 1006 may also include synthesizer circuitry 1006d for synthesizing a frequency for use by the mixer circuitry 1006a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 1006a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 1008 based on the synthesized frequency provided by synthesizer circuitry 1006d. The amplifier circuitry 1006b may be configured to amplify the down-converted signals and the filter circuitry 1 006c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 1004 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 1006a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

[0081] In some embodiments, the mixer circuitry 1006a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 1006d to generate RF output signals for the FEM circuitry 1008. The baseband signals may be provided by the baseband circuitry 1004 and may be filtered by filter circuitry 1006c. The filter circuitry 1006c may include a low-pass filter (LPF), although the scope of the embodiments is not limited in this respect.

[0082] In some embodiments, the mixer circuitry 1006a of the receive signal path and the mixer circuitry 1006a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and/or upconversion respectively. In some embodiments, the mixer circuitry 1006a of the receive signal path and the mixer circuitry 1006a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 1 006a of the receive signal path and the mixer circuitry 1006a may be arranged for direct downconversion and/or direct upconversion, respectively. In some embodiments, the mixer circuitry 1006a of the receive signal path and the mixer circuitry 1006a of the transmit signal path may be configured for super-heterodyne operation.

[0083] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 1006 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 1004 may include a digital baseband interface to communicate with the RF circuitry 1006. [0084] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the

embodiments is not limited in this respect.

[0085] In some embodiments, the synthesizer circuitry 1006d may be a fractional-N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 1006d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

[0086] The synthesizer circuitry 1006d may be configured to synthesize an output frequency for use by the mixer circuitry 1006a of the RF circuitry 1006 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 1006d may be a fractional N/N+1 synthesizer.

[0087] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 1004 or the applications processing circuit 1002 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processing circuit 1002.

[0088] Synthesizer circuitry 1 006d of the RF circuitry 1 006 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by either N or N+1 (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip- flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle. [0089] In some embodiments, synthesizer circuitry 1 006d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry 1006 may include an IQ/polar converter.

[0090] FEM circuitry 1008 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 1010, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 1006 for further processing. FEM circuitry 1008 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 1006 for transmission by one or more of the one or more antennas 1010.

[0091] In some embodiments, the FEM circuitry 1008 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include a low-noise amplifier (LNA) to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 1006). The transmit signal path of the FEM circuitry 1008 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 1006), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 1010.

[0092] In some embodiments, the UE device 1000 may include additional elements such as, for example, memory/storage, display, camera, sensor, and/or input/output (I/O) interface.

[0093] While the apparatus has been illustrated and described with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular regard to the various functions performed by the above described components or structures (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component or structure which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the invention.

[0094] Examples can include subject matter such as a method, means for performing acts or blocks of the method, at least one machine-readable medium including instructions that, when performed by a machine cause the machine to perform acts of the method or of an apparatus or system for concurrent communication using multiple communication technologies according to embodiments and examples described herein.

[0095] Example 1 is an apparatus apparatus for use in an eNodeB of a cellular network for dynamic random access channel (RACH) design comprising a processing circuit that, upon execution of instructions from a memory circuit, is configured to determine channel parameters for a RACH phase of a RACH included in a coverage area of the eNodeB based on a load information of the eNodeB, wherein the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase; and generate a system information message comprising the channel parameters for downlink transmission to one or more user equipments (UEs).

[0096] Example 2 is an apparatus including the subject matter of example 1 , wherein the processing circuit is further configured to process a random access preamble message received from a select UE of the one or more UEs during a first RAW or a subsequent RAW of the one or more sequential RAWs, when a collision criteria is satisfied, in response to the system information message.

[0097] Example 3 is an apparatus including the subject matter of examples 1 -2, including or omitting elements, wherein processing circuit is further configured to generate a contention information message comprising a broadcast message for downlink transmission to the select UE during a contention resolution period following the first RAW and the subsequent RAW of the one or more sequential RAWs, wherein the contention information message indicates a status of a receipt of the random access preamble message at the eNodeB.

[0098] Example 4 is an apparatus including the subject matter of examples 1 -3, including or omitting elements, wherein the processing circuit is further configured to generate a contention resolution information message comprising a unicast message for downlink transmission to the select UE at the end of the RACH phase, in response to receiving the random access preamble message from the select UE, wherein the contention resolution information message comprises information on a radio resource control (RRC) connection established between the select UE and the eNodeB.

[0099] Example 5 is an apparatus including the subject matter of examples 1 -2, including or omitting elements, wherein processing circuit is further configured to generate a contention resolution message comprising a unicast message for downlink transmission to the select UE at the end of the first RAW or the subsequent RAW of the one or more sequential RAWs, in response to receiving the random access preamble message from the select UE, wherein the contention resolution message comprises information on a radio resource control (RRC) connection established between the select UE and the eNodeB.

[00100] Example 6 is an apparatus including the subject matter of examples 1 -5, including or omitting elements, wherein information on one or more sequential RAWs within the RACH phase comprises one or more of a number of RAWs, a number of resources per RAW and a number of access attempts per RAW.

[00101 ] Example 7 is an apparatus including the subject matter of examples 1 -6, including or omitting elements, wherein the number of resources per RAW is tuned based on a load estimate of a respective RAW.

[00102] Example 8 is an apparatus including the subject matter of examples 1 -7, including or omitting elements, wherein the number of resources per RAW is equal to the load estimate of the respective RAW.

[00103] Example 9 is an apparatus including the subject matter of examples 1 -8, including or omitting elements, wherein the number of resources per RAW of the one or more sequential RAWs are equal. [00104] Example 10 is an apparatus including the subject matter of examples 1 -9, including or omitting elements, wherein the load estimate of the respective RAW is determined based on a performance index of a preceding RAW.

[00105] Example 1 1 is an apparatus for use in an eNodeB of a cellular network, that facilitates dynamic random access channel (RACH) design, comprising a processing circuit that, upon execution of instructions from a memory circuit, is configured to determine a load estimate of a RACH phase of a RACH that exists between the eNodeB and UEs in a coverage area of the eNodeB, comprising information on a number of active user equipments (UEs) during the RACH phase; determine a number of random access windows (RAWs) within the RACH phase, and a number of resources allocated per RAW, based on the determined load estimate; and generate a system information message comprising a broadcast message for downlink transmission to the active UEs, wherein the system information message comprises information on the number of RAWS within the RACH phase and the number of resources allocated per RAW.

[00106] Example 12 is an apparatus including the subject matter of example 1 1 , wherein the processing circuit is further configured to determine a number of access attempts for the active UEs within a RAW to attach to the network, based on the determined load estimate.

[00107] Example 13 is an apparatus including the subject matter of examples 1 1 -1 2, including or omitting elements, wherein the load estimate is determined based on a performance index of a previous RACH phase, in accordance with a predetermined relation.

[00108] Example 14 is an apparatus including the subject matter of examples 1 1 -1 3, including or omitting elements, wherein the load estimate is determined based on information from a co-existing random access technology (RAT).

[00109] Example 15 is an apparatus including the subject matter of examples 1 1 -14, including or omitting elements, wherein the load estimate is determined based on machine learning and big data techniques. [00110] Example 16 is an apparatus including the subject matter of examples 1 1 -1 5, including or omitting elements, wherein the number of RAWs within the RACH phase and the number of resources per RAW are determined further in accordance with a predetermined relation that maximizes a number of active UEs that successfully attach to the network during the RACH phase.

[00111 ] Example 17 is an apparatus including the subject matter of examples 1 1 -1 6, including or omitting elements, wherein the RACH phase comprises a single RAW.

[00112] Example 18 is an apparatus for use in a user equipment (UE) of a cellular network, that facilitates dynamic random access channel (RACH) design, comprising a processing circuit that, upon execution of instructions from a memory circuit, is configured to receive a system information message from an eNodeB associated therewith comprising channel parameters for a RACH phase of a RACH that exists between the UE and the eNodeB, wherein the channel parameters comprise

information on one or more sequential random access windows (RAWs) within the RACH phase; generate a random access preamble message for uplink transmission to the eNodeB during a first RAW of the one or more sequential RAWs, upon receiving the system information message; and selectively generate a next random access preamble message during a next RAW of the one or more sequential RAWs within the RACH phase for uplink transmission to the eNodeB, based on an information from the eNodeB that constitutes a selection criteria.

[00113] Example 19 is an apparatus including the subject matter of example 18, wherein the processing circuit is further configured to process a contention information message comprising a broadcast message received from the eNodeB during a contention resolution period following the first RAW that indicates a status of a receipt of the random access preamble message at the eNodeB during the first RAW.

[00114] Example 20 is an apparatus including the subject matter of examples 18-1 9, including or omitting elements, wherein the next random access preamble message is selectively generated when the contention information message indicates a failure of the receipt of the random access preamble message at the eNodeB during the first RAW. [00115] Example 21 is an apparatus including the subject matter of examples 18-20, including or omitting elements, wherein the next random access preamble message further comprises one or more next random access preamble messages successively generated during one or more next RAWs of the one or more sequential RAWs within the RACH phase when the contention information message associated with a preceding RAW of the one or more next RAWs indicates a failure of the receipt of the random access preamble message at the eNodeB during the preceding RAW.

[00116] Example 22 is an apparatus including the subject matter of examples 18-21 , including or omitting elements, wherein the one or more next random access preamble messages are successively generated until the one or more sequential RAWs are depleted.

[00117] Example 23 is an apparatus including the subject matter of example 18, wherein the processing circuit is further configured to process a contention resolution message comprising a unicast message received from the eNodeB during a contention resolution period following the first RAW when a collision criteria is satified, wherein the contention resolution message indicates the receipt of the random access preamble message at the eNodeB.

[00118] Example 24 is an apparatus including the subject matter of examples 18 or 23, including or omitting elements, wherein the next random access preamble message is generated when the contention resolution message is not received during the contention resolution period following the first RAW.

[00119] Example 25 is an apparatus including the subject matter of examples 18 or 23-24, including or omitting elements, wherein the next random access preamble message further comprises one or more next random access preamble messages successively generated during one or more next RAWs of the one or more sequential RAWs within the RACH phase when the contention resolution message associated with a preceding RAW of the one or more next RAWs is not received at the eNodeB during a contention resolution period following the preceding RAW.

[00120] Example 26 is a computer-readable medium comprising executable instructions that, in response to execution, cause a processor of an eNodeB to perform operations in a cellular network, the operations comprising determining a load estimate of a RACH phase of a RACH that exists between the eNodeB and UEs in a coverage area of the eNodeB, comprising information on a number of active user equipments (UEs) during the RACH phase; determining a number of random access windows (RAWs) within the RACH phase, and a number of resources allocated per RAW, based on the determined load estimate; and generating a system information message comprising a broadcast message for downlink transmission to the active UEs, wherein the system information message comprises information on the number of RAWS within the RACH phase and the number of resources allocated per RAW.

[00121 ] Example 27 is a computer-readable medium including the subject matter of example 26, wherein the processing circuit is further configured to determine a number of access attempts for the active UEs within a RAW to attach to the network, based on the determined load estimate.

[00122] Example 28 is a computer-readable medium including the subject matter of examples 26-27, including or omitting elements, wherein the load estimate is determined based on a performance index of a previous RACH phase, in accordance with a predetermined relation.

[00123] Example 29 is a computer-readable medium including the subject matter of examples 26-28, including or omitting elements, wherein the load estimate is determined based on information from a co-existing random access technology (RAT).

[00124] Example 30 is a computer-readable medium including the subject matter of examples 26-29, including or omitting elements, wherein the load estimate is determined based on machine learning and big data techniques.

[00125] Example 31 is a computer-readable medium including the subject matter of examples 26-30, including or omitting elements, wherein the number of RAWs within the RACH phase and the number of resources per RAW are determined further in accordance with a predetermined relation that maximizes a number of active UEs that successfully attach to the network during the RACH phase. [00126] Example 32 is a computer-readable medium including the subject matter of examples 26-31 , including or omitting elements, wherein the RACH phase comprises a single RAW.

[00127] Example 33 is an apparatus including the subject matter of examples 1 -1 1 , including or omitting elements, wherein the load information of the eNodeB comprises a number of UEs contending to attach to the eNodeB during the RACH phase.

[00128] Various illustrative logics, logical blocks, modules, and circuits described in connection with aspects disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other

programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform functions described herein. A general-purpose processor can be a microprocessor, but, in the alternative, processor can be any conventional processor, controller, microcontroller, or state machine.

[00129] The above description of illustrated embodiments of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such embodiments and examples, as those skilled in the relevant art can recognize.

[00130] In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding Figures, where applicable, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in breadth and scope in accordance with the appended claims below.

[00131 ] In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component or structure which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the disclosure. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.

Claims

1 . An apparatus for use in an eNodeB of a cellular network for dynamic

random access channel (RACH) design comprising a processing circuit that, upon execution of instructions from a memory circuit, is configured to:

determine channel parameters for a RACH phase of a RACH included in a coverage area of the eNodeB based on a load information of the eNodeB, wherein the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase; and

generate a system information message comprising the channel parameters for downlink transmission to one or more user equipments (UEs).

2. The apparatus of claim 1 , wherein the processing circuit is further configured to process a random access preamble message received from a select UE of the one or more UEs during a first RAW or a subsequent RAW of the one or more sequential RAWs, when a collision criteria is satisfied, in response to the system information message.

3. The apparatus of claim 2, wherein the processing circuit is further configured to generate a contention information message, comprising a broadcast message for downlink transmission to the select UE during a contention resolution period following the first RAW and the subsequent RAW of the one or more sequential RAWs, to indicate a status of a receipt of the random access preamble message at the eNodeB.

4. The apparatus of claim 3, wherein the processing circuit is further configured to generate a contention resolution information message comprising a unicast message for downlink transmission to the select UE at the end of the RACH phase, in response to receiving the random access preamble message from the select UE, wherein the contention resolution information message comprises information on a radio resource control (RRC) connection established between the select UE and the eNodeB.

5. The apparatus of claim 2, wherein the processing circuit is further configured to generate a contention resolution message comprising a unicast message for downlink transmission to the select UE at the end of the first RAW or the subsequent RAW of the one or more sequential RAWs, in response to receiving the random access preamble message from the select UE, wherein the contention resolution message comprises information on a radio resource control (RRC) connection established between the select UE and the eNodeB.

6. The apparatus of any of the claims 1 -5, wherein information on one or more sequential RAWs within the RACH phase comprises one or more of a number of RAWs, a number of resources per RAW and a number of access attempts per RAW.

7. The apparatus of claim 6, wherein the number of resources per RAW is tuned based on a load estimate of a respective RAW.

8. The apparatus of claim 7, wherein the number of resources per RAW is equal to the load estimate of the respective RAW.

9. The apparatus of claim 6, wherein the number of resources per RAW of the one or more sequential RAWs are equal.

10. The apparatus of claim 7, wherein the load estimate of the respective RAW is determined based on a performance index of a preceding RAW.

1 1 . The apparatus of any of the claims 1 -5, wherein the load information of the eNodeB comprises a number of UEs contending to attach to the eNodeB during the RACH phase.

12. An apparatus for use in an eNodeB of a cellular network for dynamic

determine a load estimate of a RACH phase of a RACH included in a coverage area of the eNodeB, comprising information on a number of active user equipments (UEs) during the RACH phase;

determine a number of random access windows (RAWs) within the RACH phase and a number of resources allocated per RAW based on the determined load estimate; and

generate a system information message comprising a broadcast message for downlink transmission to the active UEs, wherein the system information message comprises information on the number of RAWS within the RACH phase and the number of resources allocated per RAW.

13. The apparatus of claim 12, wherein the processing circuit is further configured to determine a number of access attempts for the active UEs within a RAW to attach to the network, based on the determined load estimate.

14. The apparatus of any of the claims 12-13, wherein the load estimate is determined based on a performance index of a previous RACH phase, in accordance with a predetermined relation.

15. The apparatus of any of the claims 12-13, wherein the load estimate is determined based on information from a co-existing random access technology (RAT).

16. The apparatus of any of the claims 12-13, wherein the load estimate is determined based on machine learning and big data techniques.

17. The apparatus of any of the claims 12-13, wherein the number of RAWs within the RACH phase and the number of resources per RAW are determined further in accordance with a predetermined relation that maximizes a number of active UEs that successfully attach to the network during the RACH phase.

18. An apparatus for use in a user equipment (UE) of a cellular network for dynamic random access channel (RACH) design comprising a processing circuit that, upon execution of instructions from a memory circuit, is configured to:

receive a system information message from an eNodeB associated therewith comprising channel parameters for a RACH phase of a RACH between the UE and the eNodeB, wherein the channel parameters comprise information on one or more sequential random access windows (RAWs) within the RACH phase;

generate a random access preamble message for uplink transmission to the eNodeB during a first RAW of the one or more sequential RAWs, upon receiving the system information message; and selectively generate a next random access preamble message during a next RAW of the one or more sequential RAWs within the RACH phase for uplink

transmission to the eNodeB, based on an information from the eNodeB that constitutes a selection criteria.

19. The apparatus of claim 18, wherein the processing circuit is further configured to process a contention information message comprising a broadcast message received from the eNodeB during a contention resolution period following the first RAW that indicates a status of a receipt of the random access preamble message at the eNodeB during the first RAW.

20. The apparatus of claim 19, wherein the next random access preamble message is selectively generated when the contention information message indicates a failure of the receipt of the random access preamble message at the eNodeB during the first RAW.

21 . The apparatus of claim 20, wherein the next random access preamble message further comprises one or more next random access preamble messages successively generated during one or more next RAWs of the one or more sequential RAWs within the RACH phase when the contention information message associated with a preceding RAW of the one or more next RAWs indicates a failure of the receipt of the random access preamble message at the eNodeB during the preceding RAW.

22. The apparatus of claim 21 , wherein the one or more next random access preamble messages are successively generated until the one or more sequential RAWs are depleted.

23. The apparatus of claim 18, wherein the processing circuit is further configured to process a contention resolution message comprising a unicast message received from the eNodeB during a contention resolution period following the first RAW when a collision criteria is satisfied, wherein the contention resolution message indicates the receipt of the random access preamble message at the eNodeB.

24. The apparatus of claim 23, wherein the next random access preamble message is generated when the contention resolution message is not received during the contention resolution period following the first RAW.

25. The apparatus of claim 24, wherein the next random access preamble message further comprises one or more next random access preamble messages successively generated during one or more next RAWs of the one or more sequential RAWs within the RACH phase when the contention resolution message associated with a preceding RAW of the one or more next RAWs is not received at the eNodeB during a contention resolution period following the preceding RAW.