WO2011049430A2

WO2011049430A2 - Method for optimizing quality of multicast stream over wireless access point

Info

Publication number: WO2011049430A2
Application number: PCT/MY2010/000219
Authority: WO
Inventors: Mohd Ariff Abdullah; Muhammad Faheem Mohd Ezani; Shariq Haseeb; Gopinath Rao Sinniah
Original assignee: Mimos Berhad
Priority date: 2009-10-23
Filing date: 2010-10-22
Publication date: 2011-04-28
Also published as: WO2011049430A3; MY157644A

Abstract

A method of optimizing the quality of multicast services over a wireless network by dynamically controlling a broadcast rate, comprising: suppressing an automatic rate fallback protocol so that a broadcast data rate is not limited to the base data rate; transmitting a multicast data stream from an access point to a plurality of nodes; detecting if there is any data loss in the said multicast data stream; and lowering the data rate for each node incrementally if there is any data loss, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first.

Description

Method For Optimizing Quality Of Multicast Stream Over Wireless Access

Point

FIELD OF INVENTION

The present invention generally relates to a wireless multicast method, and particularly relates to a method of optimizing the quality of multicast streams over a wireless access point.

BACKGROUND OF THE INVENTION

Lately, Internet use has shifted to applications that deliver large files such as music, video and other types of multimedia. Use of wireless communication as an access link has an advantage in that information delivery services can be provided to users without bearing the infrastructure cost of wired connections. If music or video contents can be delivered through a network that includes wireless routes as an access link, the resulting merits are substantial. However, if the system is configured such that one-to-one communication is carried out between the wireless base station and each of the wireless terminals, the same information having the same contents needs to be delivered through separate channels to individual wireless terminals that are requesting the service. Such a configuration does not make efficient use of communication resources. A wireless transfer of data streams using multicasting typically delivers information such as music and video contents through wireless routes by transmitting singular multicast content from a base station or access point to a plurality of wireless terminal nodes, and these nodes simultaneously receive the multicast content. Multicast transmission is substantially more efficient compared to a plurality of unicast transmissions, providing that the system is able to broadcast to the plurality of nodes. Because frequency spectrum for wireless services is limited and costly to expand, multicast services have become very appealing to wireless service providers.

One problem with multicast services is the bottleneck in rate of data transfer that occurs because the standard wireless access points do not recognize multicast traffic, and send the multicast packets of data as broadcast packets. Since broadcast is used mainly for operational and maintenance purposes, the data rate for broadcast packets is limited to the lowest rate of the access point. Multicast traffic is inherently different because it contains packets of typically large capacity data including music and video.

Accordingly, there is a need for a method of optimizing the quality of the multicast service by increasing the data transfer rate.

SUMMARY OF THE INVENTION

This invention relates to a method of optimizing the quality of multicast services over a wireless network by increasing the rate at which the multicast stream is transmitted. The method comprises dynamically setting a broadcast rate at which the multicast stream is transmitted by suppressing an automatic rate fallback (ARF) protocol so that the broadcast rate is not limited to the minimum data rate between an access point and terminal nodes of the wireless network. This invention also relates to a method of optimizing data rates for wireless multicast traffic between at least one access point and a plurality of nodes having a plurality of operable rates, comprising the steps of:

a) suppressing an ARF protocol so that a broadcast data rate between said at least one access point and said plurality of nodes is not limited to a minimum of the said plurality of operable rates; b) transmitting a multicast data stream from the said access point to the said plurality of nodes;

c) detecting if there is any data loss in the said multicast data stream; and

d) lowering the data rate for each node incrementally over the said plurality of rates, if there is any data loss, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first. This invention further relates to a method of optimizing data rates for wireless multicast traffic between at least one access point and a plurality of nodes having a plurality of operable rates, comprising the steps of:

a) suppressing an ARF protocol so that a broadcast data rate between said at least one access point and said plurality of nodes is not limited to a minimum of the said plurality of operable rates;

b) transmitting a multicast data stream from the said access point to the said plurality of nodes;

c) detecting if there is any data loss in the said multicast data stream; d) determining if the said data loss is caused by link error; and e) lowering the data rate for each node incrementally over the said plurality of rates, if there is any data loss caused by link error, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first. This invention also relates to a wireless multicasting system that optimizes the quality of multicast services over a wireless network comprising: at least one access point for transmitting data streams received from a source at a plurality of operable rates, including a broadcast data rate; a plurality of nodes adapted to link to and receive the data streams; and a means of dynamically controlling broadcast data rate. This controlling of the broadcast data rate is achieved by suppressing an ARF protocol so that the broadcast data rate is not limited to the minimum rate between the access point and the nodes. The ARF automatically lowers the broadcast data rate when there is a client that needs to operate at a lower rate, for example when there are noise signals causing link errors, which do not allow the data stream to be sent at higher rates. When the broadcast rate is lowered, so is the multicast stream rate. This invention proposes to stop the ARF protocol from limiting the broadcast data rate to the minimum data rate in the wireless network. The multicast stream rate is initially set to the maximum rate. If there is a poor connection or link error resulting in data loss, the multicast stream rate transmitted to each node is lowered over the plurality of operable rates until the data loss reaches an acceptable level or until the minimum rate is reached, whichever is first. In a preferred embodiment, the access point determines that the data loss is caused by link error and not other factors such as collision. This is achieved by a feedback from the nodes to the access point. This feedback may either be an ACK frame or a NAK frame. An ACK frame received by the access point means that the node has received the data packet without any error. If the node sends a NAK frame, it means that the packets sent to the node contain an error and need to be sent again. However, if neither ACK nor NAK is received by the access point upon sending a data packet, then it is likely that the packets have been lost due to collision. The access point then sets a back off timer before sending the packets again to avoid another collision. A data collision is not a link error, and does not necessitate a lowering of the data rate.

This invention further relates to a wireless multicasting system that optimizes the quality of multicast services over a wireless network comprising: at least one access point, said access point able to transmit data streams received from a source at a plurality of operable rates, including a broadcast data rate; and a plurality of nodes adapted to link to and receive data streams from the access point such that the broadcast data rate can be manually set to any of the operable rates. The access point still initially transmits at the maximum data rate to the nodes, until there is data loss between said access point and any said node, upon which the data rate is lowered to a lower rate until the data loss in minimized or the rate that was manually set is reached. In a preferred embodiment, the access point determines that the data loss is caused by link error and not other factors such as collision. This is achieved by a feedback from the nodes to the access point. This feedback may either be an ACK frame or a NAK frame. An ACK frame received by the access point means that the node has received the data packet without any error. If the node sends a NAK frame, it means that the packets sent to the node contain an error and need to be sent again. However, if neither ACK nor NAK is received by the access point upon sending a data packet, then it is likely that the packets have been lost due to collision. The access point then sets a back off timer before sending the packets again to avoid another collision. A data collision is not a link error, and does not necessitate a lowering of the data rate. As an example, if a private network is used to forward large multicast streams, the minimum rate can be set very high, at the cost of the coverage area. However, if the multicast stream is relatively small, minimum rate can be set very low, thus allowing the access point to serve a larger area. This is an improvement over the current method whereby the access point serves a constant width of coverage and various data rates statically, and regardless of the distance from the client nodes. This is highly inefficient, especially if the distance between access point and nodes is very small.

In a preferred embodiment, the methods and systems described above operate within the 802.1 1 protocol. In another preferred embodiment, the methods and systems described above operate with wireless network attachment points using the 801.1 1 technology.

Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows a flowchart depicting a process flow in an embodiment of this invention.

Figure 2 shows a diagram of a wireless network in an embodiment of this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to Figures 1 and 2, there can be seen a method of optimizing data rates for wireless multicast traffic in a wireless network between at least one access point (10) and a plurality of nodes (20). The wireless data streams sent over the wireless network can be at any of a plurality of operable rates. A broadcast rate is usually limited to the lowest operable rate, and is used mainly for operational or maintenance purposes. In the case of the wireless access point not recognizing multicast data, the multicast data is sent on broadcast data rates. Typical wireless networks employ Automatic Rate Fallback (ARF) mechanisms or protocols to limit the broadcast rate to the minimum. As part of the method of this invention, the ARF protocol is disabled so the broadcast data rate is not limited to the minimum rate.

In order to deal with link error data loss caused by overly high data rates, there is shown in Figure 1 a feedback method that allows the data rate to remain at a higher rate until data loss occurs. The rate is initially set to maximum, in {Set R=Rmax}, and a counter is set to minimum {Set C=Cmin} and the data frame is transmitted {Send data frame}. After this, the wireless access point (10) checks to see is a NAK is received {NAK received?}. The NAK is sent by the receiving terminal node (20) only when the data packet received contains an error and needs to be resent. If no NAK is received by the access point (10), the wireless point (10) checks to see if an ACK is received {ACK received?} from the node (20). An ACK sent by the node (20) to the access point (10) means that the data was received without error, and the rate can be increased if not yet at maximum, and maintained if already at maximum. If ACK is not received, there is a high probability that data loss has occurred due to collision. In this case, a back-off timer is set {Start back off timer} before the data packet is sent again to reduce the risk of another collision. If ACK is received, the access point (10) checks if the rate is already at maximum {R=Rmax?}, in which case the rate is maintained. If the rate is not yet at maximum, the access point (10) increases the rate of the next data packet {R=Rnext}, and the process repeats by setting the counter to minimum again {C=Cmin} and sending another data frame or packet.

In the case that NAK is received, this usually means the data loss is due to link error. The counter is increased {C=C+1 } and checked if already at maximum {C=Cmax?}. If the counter is not yet at maximum, the cycle is repeated and the data frame or packet is sent again. However, if the counter has reached maximum, the rate is checked if it is already at minimum {R=Rmin?}. If the minimum rate has been reached, the packets are dropped and the node connection is cut {DROP}. If the minimum rate is not yet reached, the rate is set to the next lower rate {R=Rprev} and the counter reset to minimum {C=Cmin} before the cycle starts over. In this way, data packets not received due to link error can be tried to be sent a predetermined number of times, C, before the rate is lowered to the next lowest rate and the sending is tried again. It should be noted that the invention has been described with reference to a few exemplary and preferred embodiments in order to demonstrate the principles and concepts of the invention. The invention is not limited to the embodiments described herein. As will be understood by those skilled in the art, modifications may be made to the embodiments described herein and all such modifications are within the scope of the invention.

Claims

A method of optimizing data rates for wireless multicast traffic between at least one access point (10) and a plurality of nodes (20) having a plurality of operable rates, comprising the steps of:

a) suppressing an automatic rate fallback protocol so that a broadcast data rate between said at least one access point (10) and said plurality of nodes (20) is not limited to a minimum of the said plurality of operable rates;

b) transmitting a multicast data stream from the said access point (10) to the said plurality of nodes (20);

c) detecting if there is any data loss in the said multicast data stream; and

d) lowering the data rate for each node (20) incrementally over the said plurality of rates, if there is any data loss, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first.

c) detecting if there is any data loss in the said multicast data stream; d) determining if the said data loss is caused by link error; and e) lowering the data rate for each node (20) incrementally over the said plurality of rates, if there is any data loss caused by link error, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first.

A method of optimizing data rates for wireless multicast traffic between at least one access point (10) and a plurality of nodes (20) having a plurality of operable rates according to claims 1 or 2, wherein the said wireless multicast traffic operates within the 802.1 1 set of standards.

A wireless multicasting system that optimizes the quality of multicast services over a wireless network comprising:

at least one access point (10), said access point able to transmit data streams received from a source at a plurality of rates, and including a broadcast data rate;

a plurality of nodes (20), said plurality of nodes adapted to link to and receive said data streams from said access point (10); and

a means of dynamically controlling said broadcast data rate

characterized in that said means comprises suppressing an automatic rate fallback protocol so that the said broadcast data rate is not limited to the minimum rate between said access point (10) and said nodes (20).

A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to claim 4 wherein said means further comprises a means of detecting if there is data loss occurring in the said data stream.

A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to claim 5 further comprising a means of lowering the data rate for each node (20) over the said plurality of rates, if there is any data loss, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first.

7. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to claim 5 further comprising a means of determining if any data loss occurring in the said data steam is caused by link errors.

8. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to claim 7 further comprising a means of lowering the data rate for each node (20) over the said plurality of rates, if there is any data loss caused by link errors, until the data loss reaches an acceptable level or until the said minimum rate is reached, whichever happens first.

9. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to any of claims 4 through 8 wherein the said wireless multicast traffic operates within the 802.11 set of standards.

10. A wireless multicasting system that optimizes the quality of multicast services over a wireless network comprising:

at least one access point (10), said access point able to transmit data streams received from a source at a plurality of rates, and including a broadcast data rate; and

a plurality of nodes (20), said plurality of nodes adapted to link to and receive data streams from said access point (10)

characterized in that said broadcast data rate can be manually set to any of the said plurality of rates.

1 1. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to claim 10 wherein the said manual set of the broadcast data rate comprises setting the access point (10) to initially transmit at a maximum data rate to the said nodes (20), until there is data loss between said access point and any said node, upon which the data rate is successively lowered to a lower rate until the data loss reaches an acceptable level or until the said manually set rate is reached, whichever happens first.

12. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to claims 10 or 1 1 , wherein the data rate is set to a rate close to maximum when said data stream is large.

13. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to any of claims 10 through 12, wherein the data rate is set to a rate close to minimum when said data stream is small.

14. A wireless multicasting system that optimizes the quality of multicast services over a wireless network according to any of claims 4 through 13 wherein the said wireless multicast traffic operates within the 802.1 1 set of standards.