Method for link buffer size and queue length estimation for bandwidth-varying mobile data networks
A sum-of-delays algorithm in a digital mobile communication bandwidth-varying network is employed to estimate link buffer size and queue length in an undying network connection. In particular, mechanisms associated with the process compensate for link bandwidth variations. In a particular embodiment, passive estimation are employed to implement the process by simply measuring the in-band data packet timings to perform estimation, thus eliminating the need for transmission of extra measurement packets. This method enables the integration of the link buffer size estimation algorithm into existing transport protocols such as TCP to optimize flow and congestion controls. As part of the invention, a new congestion control method called TCP Queue-length-Adaptive (TCP-QA) is developed to employ the sum-of-delays algorithm in the TCP sender computer to control the data flow in a TCP connection. Compared to existing TCP variants, TCP-QA can achieve significantly better network bandwidth utilization in bandwidth-varying networks.
1. A method operative in a digital computer comprising:
estimating packet transmission delays of packets sent via a wireless network subject to variable bandwidth;
estimating queuing delays of packets sent via the wireless network between a sender and a receiver, with compensation for variations in packet transmission delays; and
estimating network queue length from a sum of the packet transmission delays and the queuing delays,
wherein said sum of packet transmission delays comprises a measurement of in-band data and ACK packet timings in passive estimation to eliminate need for transmission of extra measurement packets.
2. A method operative in a digital computer comprising:
estimating packet transmission delays of packets sent via a wireless network subject to variable bandwidth;
estimating queuing delays of packets sent via the wireless network between a sender and a receiver, with compensation for variations in packet transmission delays; and
estimating network queue length from a sum of the packet transmission delays and the queuing delays,
wherein the queuing delays are estimated from an upper bound and a lower bound computed from packet transmission delays and round-trip times.
3. The method according to claim 2 wherein the upper bound of queuing delays is computed from the sum of packet transmission delays.
4. The method according to claim 2 wherein the lower bound of queuing delay for a packet is computed from its round-trip times, the minimum round-trip time, and its transmission delay.
5. A method operative in a digital computer comprising:
estimating packet transmission delays of packets sent via a wireless network subject to variable bandwidth;
estimating queuing delays of packets sent via the wireless network between a sender and a receiver, with compensation for variations in packet transmission delays; and
estimating network queue length from a sum of the packet transmission delays and the queuing delays,
wherein the network queue length is computed from the lower bound wherein the upper bound of queuing delays is computed from the sum of packet transmission delays and wherein the upper bound of queuing delay for a packet is computed from its round-trip times, the minimum round-trip time, and its transmission delay.
6. A method operative in a digital computer comprising:
estimating packet transmission delays of packets sent via a wireless network subject to variable bandwidth;
estimating queuing delays of packets sent via the wireless network between a sender and a receiver, with compensation for variations in packet transmission delays; and
estimating network queue length from a sum of the packet transmission delays and the queuing delays,
wherein said sum of packet transmission delays comprises measuring in-band data and ACK packet timings in passive estimation to eliminate need for transmission of extra measurement packets.
7. A method operative in a computer comprising:
estimating the packet transmission delays of packets sent via a wireless network;
estimating the queuing delays of packets sent via said network between a sender and a receiver, with compensation for variations in the packet transmission delays by using measurements of packet transmission time at a bottleneck link;
estimating the network queue length from the sum of the packet transmission delays and the queuing delays; and
estimating the network link buffer size from the estimated queue lengths in order to provide a sum-of-delays method that incorporates effects of bandwidth variations wherein the queuing delays are estimated from an upper bound and a lower bound computed from packet transmission delays and round-trip times.
8. The method according to claim 7 wherein the upper bound of queuing delays is computed from the sum of packet transmission delays.
9. The method according to claim 7 wherein the lower bound of queuing delay for a packet is computed from its round-trip times, the minimum round-trip time, and its transmission delay.
10. The method according to claim 7 wherein the network link buffer size is estimated from taking the maximum of all the queue length estimates.
11. A method according to claim 7 wherein results of said estimation of queue length with compensation for variations in packet transmission delays is used for congestion control in a communications protocol.
12. The method according to claim 11 incorporated into a transport protocol.
13. The method according to claim 11 incorporated into a transport protocol TCP-QA which is implemented at the sender only and is compatible with existing standard TCP receivers.
14. The method according to claim 13 comprising executing the following steps for TCP's congestion avoidance phase (TCP_QA_CA( )), for updating TCP's slow-start threshold (TCP_QA_SSTH( )), and for the initialization phase (TCP_QA_INIT( )):
TCP_QA_CA()
TCP_QA_SSTH()
{
{
if (Queue_length < target_qs)
if(packet_loss_event)
//burst start phrase
{
cwnd=cwnd+1
if (Queue_length > target_qs)
else
cwnd = cwnd / 2
{
}
//slow decrement phrase
}
cwnd
=
cwnd
-
1
cwnd
TCP_QA_INIT()
}
{
}
// burst init phrase
if (burst_start_enabled)
cwnd = min(awnd, 64)
}.