SYSTEMS AND METHODS FOR DISTRIBUTED UNIT OR CENTRALIZED UNIT FLOW CONTROL OPTIMIZATIONS FOR HIGHLY SCALABLE CELLULAR SYSTEMS
System and methods for Distributed Unit (DU) or Centralized Unit (CU) flow control optimizations for highly scalable cellular systems. A DU is configured to indicate to CU if a specific Data Radio Bearer (DRB) is not getting adequate latency or throughput. Frequency of Downlink Data Delivery Status (DDDS) is increased for some such DRBs and can be decreased for other DRBs if needed. A buffer management method module is configured to improve scalability of a Base Station. Implementations of these operations can be configured for and located at a Radio Access Network Intelligent Controller.
1 . A method for a radio access network (RAN) base station (BS) comprising:
selecting a subset of Data Radio Bearers (DRBs) from a set of DRBs;
changing a frequency of DL Data Delivery Status (DDDS) message transmissions for the subset of DRBs; and
maintaining a frequency or reducing the frequency of DDDS transmissions for remaining DRBs of the set of DRBs.
2 . The method of claim 1 , further comprising:
reducing the frequency of the DDDS message transmissions for the subset of DRBs; and
maintaining a frequency of the DDDS transmissions for remaining DRBs of the set of DRBs.
3 . The method of claim 1 , further comprising:
increasing the frequency of the DDDS message transmissions for the subset of DRBs; and
maintaining a frequency or reducing the frequency of the DDDS transmissions for remaining DRBs of the set of DRBs.
4 . The method of claim 1 , wherein the method is implemented at a RAN Intelligent Controller (RIC) configured to identify the subset of DRBs based on parameters sent from a Distributed Unit (DU) or a Centralized Unit (CU) of the BS.
5 . The method of claim 4 , further comprising:
subscribing to the parameters from a gNB or eNB E2 node by a near-RT RIC
detecting, by the E2 node, an RIC event trigger;
analyzing the parameters, by the near-RT RIC, to determine whether to change a frequency of the subset of DDDS transmissions, and if so;
updating the parameters at the E2 node.
6 . The method of claim 4 , wherein the parameters comprise:
a number of DRBs, total memory available for these DRBs; and
for each of the DRBs or for the subset DRBs, the parameters comprise:
a sample of PDU lengths received for that DRB at DU during a time interval,
time instants when DDDS is sent from DU to CU-UP for that DRB,
information from DDDS for that DRB,
an average RLC queueing delay in DU for that DRB,
an average queuing delay in CU-UP for that DRB,
a Mid-haul delay,
a memory wastage or utilization for that DRB at DU, or
a memory wastage or utilization for that DRB at CU, or
any combination of thereof.
7 . The method of claim 6 , wherein the parameters comprise:
sending output parameters from the RT RIC to the CU, the DU, or both, including:
an identity of DRBs for which DDDS needs to be sent more often and a decreased time interval;
an identity of DRBs for which DDDS needs to be sent less often and an increased time interval; or
updated buffer management pools for the subset of DRBs;
or a combination of thereof.
8 . A method for a radio access network (RAN) base station (BS) comprising a Distributed Unit (DU) and a Centralized unit (CU):
indicating at DU if a DRB is not getting a required latency or throughput;
determining, at the DU, if a waiting time of Radio Link Control (RLC) Service Data Units (SDUs) in queues at the DU exceeds a threshold criterion for a number of packets; and
if so, indicating by the DU to the CU that the threshold criterion is exceeded.
9 . The method of claim 8 , further comprising:
maintaining, by the DU, a latency condition state variable configured to indicate a high or low latency state.
10 . The method of claim 9 , wherein the DU is configured to set a DDDS Protocol Data Unit (PDU) bit to indicate the latency condition when the latency is in the high condition.
11 . The method of claim 8 , further comprising:
reducing a frequency of DDDS message transmissions for the DRB if the threshold criterion is exceeded.
12 . A method for a radio access network (RAN) base station (BS) comprising a Distributed Unit (DU) and a Centralized unit (CU) comprising:
configuring a 4G eNB DU to increase a frequency of DDDS messages to a CU upon finding holes in a received Packet Data Convergence Protocol (PDCP) SNs.
13 . A system comprising:
a base station (BS) comprising a buffer management module, the buffer management module being configured to take a vector of inputs and output buffer management parameters to compute a wastage for a buffer size for each DRB and an average memory wastage across a plurality of DRBs.
14 . The system of claim 13 , wherein the buffer management module is further configured to at least
give the output as (b 1 , b 2 , . . . , b K , M 1 , M 2 , . . . , M K ); and
vector of inputs includes:
a sample of PDU lengths for each DRB,
total memory being made available for storing the PDUs of each DRB,
5QI of each DRB, or
total number of DRBs to be supported; or
or any combination thereof.
15 . The system of claim 14 , wherein for a PDU of length L assigned to a buffer of size b, memory wastage is defined as (b−L) bytes, or memory utilization is defined as L/b;
and the buffer management module is configured to at least estimate the average memory wastage considering all of the plurality of DRBs.
16 . The system of claim 15 , wherein the buffer management module is configured to at least estimate the average memory wastage for each buffer size separately.
17 . The system of claim 13 , wherein the buffer management module is configured to at least:
partition a total memory of M bytes is partitioned into K pools, where the i th memory pool consists of M i buffers each of size b i bytes;
take a sample of T PDU lengths X 1 , X 2 , . . . , X T at DU for a DRB, where each of the T PDUs are to be assigned to a buffer having a size one of the K different values; wherein K is smaller than T for one or more applications; and
calculate empirical probabilities p i for each of the K buffer sizes, where 1<=i<=K, so that where a plurality of the PDUs get assigned to a buffer of the same size;
where Y i denotes an i th maximum of the sample X 1 , X 2 , . . . , X T , so that Y 1 is the PDU length that occurred the maximum number of times, Y 2 is the next PDU length after Y 1 that occurred the maximum number of times, and so on to Yn, and Y (1) , Y (2) , . . . , Y (K) is the increasing-ordered sequence of Y 1 , Y 2 , . . . , Y K , the size of each buffer of type i is estimated as b i =Y (i) +μ i , μ being configurable a small factor in bytes, and a number of the buffers to be M i are estimated and set it equal to Ceil(p i *M/b i ).
18 . The system of claim 17 , wherein the buffer management modules is configured with a maximum number of buffers for a DRB.
19 . The system of claim 18 , wherein the buffer management module is configured with a RLC SDU queue of size (RlcSduQSize) for each DRB, and calculating the maximum number of buffers for each buffer size the RlcSduQSize comprises:
first calculating empirical probabilities p i for each of the K PDU lengths, where 1<=i<=K.;
calculating the probability q i ;
summing the PDU of length h to be assigned a buffer of size b i p h , taking PDU of length h from the set of PDUs with PDU length K; and
assigning Ceil(q i *RlcSduQSize) buffers of size b i should for the DRB.
20 . The system of claim 13 , wherein the buffer management module is implemented a Distributed Unit (DU) or a Centralized unit (CU).
21 . The system of claim 13 wherein the buffer management module is connected to an RIC, and the RIC is configured to implement actions for the buffer management module.