Dynamic TCP layer optimization for real-time field performance

Patent metadata

Field	Value
Publication number	US-9380635-B2
Application number	US-201213346070-A
Country	US
Kind code	B2
Filing date	Jan 9, 2012
Priority date	Jan 9, 2012
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

A method and system that mitigates data session degradation over a radio link connection with an end server by allocating resources at a wireless communication device based on real-time radio frequency (RF) channel conditions. A performance tracking and resource allocation (PTRA) logic monitors radio access bearer (RAB) configuration and radio link quality for communication links between the WCD and the end server. The PTRA logic sets a maximum transmission unit (MTU) size parameter to a pre-established size associated with the measured radio link quality. In response to detecting a change in the RAB configuration, the PTRA logic performs a real-time round trip time (RTT) measurement utilizing individual RTTs associated with packet segments transmitted at a lower protocol layer. In addition, the PTRA logic modifies at least one of a transmission control protocol (TCP) receive window (RWIN) and a TCP transmit window (TWIN) using the real-time RTT measurements and RAB configuration.

First claim

What is claimed is:

1. In a wireless communications device (WCD), a method for mitigating transmission control protocol (TCP) data session degradation over a radio link connection with an end server, the method comprising:
monitoring a bandwidth allocation for at least one of an uplink communication and a downlink communication with the end server;
detecting a change in the bandwidth allocation, wherein detecting the change in the bandwidth allocation comprises determining whether a change in at least one of an uplink radio access bearer (RAB) configuration and a downlink RAB configuration has occurred;
in response to detecting the change in the bandwidth allocation, performing a real-time round trip time (RTT) measurement utilizing round trip time intervals corresponding to segments of a User Datagram Protocol (UDP) datagram being transmitted at a lower protocol layer; and
modifying at least one of a TCP receive window (RWIN) and a TCP transmit window (TWIN) using the real-time RTT measurement.

2. The method of claim 1 , wherein:
the uplink RAB configuration provides an uplink maximum bandwidth and an allowed uplink frame size, wherein the downlink RAB configuration provides a downlink maximum bandwidth and an allowed downlink frame size, and wherein the uplink maximum bandwidth and the downlink maximum bandwidth constitute the bandwidth allocation; and
performing the real-time RTT measurement comprises determining the real-time RTT utilizing lower-layer RTTs for packet segments transmitted at one of a radio link control (RLC) layer, a Radio Link Protocol (RLP) layer, a Packet Data Convergence Protocol (PDCP) layer and a Hybrid Automatic Repeat-Request (HARD) protocol layer.

3. The method of claim 2 , wherein said determining a real-time RTT further comprises:
selecting a first sample size for a sequence of protocol data units (PDUs) that are transmitted at a lower protocol layer, wherein said first sample size falls within a range of values between a pre-established minimum sample size and a pre-established maximum sample size, wherein the sequence of PDUs having the first sample size represents a subset of a complete set of PDUs having a second, larger sample size at the lower protocol layer, which complete set of PDUs are segments of a single IP layer packet generated at an IP layer, and wherein the first sample size corresponds to a first number of PDUs whose lower-layer RTTs are sufficient to provide an estimated real-time RTT that is expected to be within a specific range of an actual RTT generated at the TCP layer for the single IP layer packet.

4. The method of claim 3 , further comprising:
computing (a) a partial RTT sum that includes a summation of the first number of individual lower-layer RTTs corresponding to transmission and acknowledgement of each of the first number of individual PDUs within the sequence of PDUs of the sample size and (b) a corresponding wait time latency sum of sequential latency intervals between receipt of an acknowledgement of a successful transmission of a preceding PDU in the sequence and subsequent transmission of a next PDU in the sequence of PDUs of the first sample size; and
calculating a current estimate of real-time RTT by: extrapolating the partial RTT sum associated with the sample size to an estimated RTT sum for the complete set of PDUs corresponding to the single IP layer packet; extrapolating the corresponding wait time latency sum to an estimated wait time latency sum associated with the complete set of PDU; and adding the estimated RTT sum to the estimated wait time latency sum to obtain a real-time RTT; and
assigning the real-time RTT for utilization as a current TCP RTT for processes at the WCD involving the current TCP RTT.

5. The method of claim 2 , further comprising:
determining a bandwidth delay product (BDP) providing a measure of an amount of data that is within the radio frequency (RF) communication channel between the WCD and the end server at a corresponding time instant, wherein said BDP is determined based on the real-time RTT and an uplink and a downlink maximum channel rate associated with a corresponding maximum bandwidth from an RAB configuration, wherein the BDP includes an uplink BDP component and a downlink BDP component;
automatically re-configuring at least one of (a) a size for a TCP receive window (RWIN) and (b) a size for a TCP transmit window (TWIN) based on a corresponding BDP; and setting a value for a maximum transmission unit (MTU) size parameter for the RF communication link using previously established associations between radio link quality RAB assignment.

6. The method of claim 1 , further comprising:
measuring a radio link quality for a downlink communication channel of the WCD;
retrieving a data structure that provides pre-established associations between radio link quality and at least one of: (a) maximum transmission unit (MTU) size parameter; (b) TCP transmit data buffer size parameter; and (c) TCP receive data buffer size parameter;
determining a range from among a plurality of radio link quality ranges in which the radio link quality falls; and
in response to the radio link quality being within a first range of a plurality of radio link quality ranges: (a) setting an MTU size for packet transmission to a first size that is associated with the first range of the plurality of radio link quality ranges; (b) setting a TCP transmit data buffer size parameter to a transmit buffer size that is associated with the first range of radio link quality ranges; and (c) setting a TCP receive data buffer size parameter to a receive data buffer size that is associated with the first range of the plurality of radio link quality ranges.

7. The method of claim 6 , wherein:
the plurality of radio link quality ranges are used to provide a level of control sensitivity for resource allocation based on radio link quality; and
the method further comprises:
in response to the radio link quality being within the first range of the plurality of radio link quality ranges, setting an MTU size to a first size;
monitoring for a change in the radio link quality;
automatically adjusting the size of the MTU in real-time in response to detecting a change in the radio link quality that moves a current signal quality from being within one pre-established radio link range to a different radio link quality range among the plurality of radio link quality ranges, wherein each of the plurality of radio link quality ranges is associated with a corresponding pre-determined size to be utilized for the MTU.

8. The method of claim 6 , further comprising:
monitoring the radio link quality and the channel bandwidth allocation before and after an establishment of a data connection between the WCD and the end server; and
responding to changes in the radio link quality by setting at least one of the MTU size, the TCP transmit buffer size parameter, and the TCP receive buffer size parameter during one of: (a) a current socket connection with the end server; (b) a next socket connection with the end server; and (c) a next handshake procedure with the end server; and
wherein said modifying at least one of a TCP receive window (R WIN) and a TCP transmit window (TWIN) occurs during one of: (a) the current socket connection with the end server; (b) the next socket connection with the end server; and (c) the next handshake procedure with the end server.

9. In a wireless communications device (WCD), a method comprising:
measuring a radio link quality for a downlink communication channel of the WCD, wherein said measured radio link quality falls within a first range of a plurality of radio link quality ranges;
determining that a change in at least one of an uplink radio access be

Assignees

• Chisu Daniel C
• Declerck Daniel J
• Google Technology Holdings LLC

Inventors

• Chisu Daniel C
• Declerck Daniel J

Classifications

• H04W80/06 Primary

  Transport layer protocols, e.g. TCP [Transport Control Protocol] over wireless {(transmission control protocol/Internet protocol [TCP/IP] or user datagram protocol [UDP] H04L69/16)} · CPC title