Receiver which mimics degraded radio conditions when buffer overflow conditions are met
Methods and apparatus for providing a flow control mechanism in a wireless network are described. In order to force a transmitting station to implement a rate adaptation mechanism, in which speed is traded off for reliability, a receiver within a receiving station behaves as if the radio conditions were degraded. This may be implemented when defined criteria are met, such as when the available buffer space falls below a threshold, and for some or all types of frames. In an embodiment, when the criteria are met, the receiver does not acknowledge frames received at one or more higher data rates.
1. A method of operating a wireless receiver comprising:
receiving frames from a wireless transmitting station; and
when buffer overflow conditions are met, mimicking degraded radio conditions for at least a subset of the frames received to induce a rate adaptation mechanism at the transmitting station;
wherein mimicking degraded radio conditions comprises:
stopping acknowledging of at least a subset of the frames received at one or more data rates by applying a mask to a list of accepted data rates to remove the one or more data rates from the list, the mask defining at least one of a set of rates to be excluded from the list of accepted data rates or a set of rates which are to be included within the list of accepted data rates, wherein the mask is applied for frames exceeding a threshold size; and
dropping the frames exceeding the threshold size according to the masked list of accepted data rates,
wherein the one or more data rates do not include a data rate at which beacons are transmitted and do include all mandatory data rates which exceed the data rate at which beacons are transmitted.
2. A method according to claim 1 , wherein the buffer overflow conditions are defined in terms of one or more of: input data rate, output data rate, and available buffer space.
3. A method according to claim 2 , wherein a portion of the available buffer space is reserved for traffic types which are not retransmitted.
4. A method according to claim 1 , further comprising modifying the mask defining one of: a set of rates to be excluded from the list of accepted data rates and a set of rates which are to be included within the list of accepted data rates, based on one or more parameters.
5. A method according to claim 1 , wherein the mask is further applied for frames with a lower priority or lower QoS type.
6. A device comprising:
a wireless receiver; and
a buffer,
wherein the wireless receiver is arranged to:
receive frames from a wireless transmitting station; and
when buffer overflow conditions are met, to mimic degraded radio conditions for at least a subset of the frames received to induce a rate adaptation mechanism at the transmitting station;
wherein mimicking degraded radio conditions comprises:
stopping acknowledging of at least a subset of the frames received at one or more data rates by applying a mask to a list of accepted data rates to remove the one or more data rates from the list for frames which exceed a predetermined size, the mask defining at least one of a set of rates to be excluded from the list of accepted data rates or a set of rates which are to be included within the list of accepted data rates, wherein the mask is applied for frames exceeding a threshold size; and
dropping the frames exceeding the threshold size according to the masked list of accepted data rates,
wherein the one or more data rates do not include a data rate at which beacons are transmitted and do include all mandatory data rates which exceed the data rate at which beacons are transmitted.
7. A device according to claim 6 , wherein the buffer overflow conditions are defined in terms of one or more of: input data rate, output data rate, and available space in the buffer.
8. A device according to claim 6 , wherein the device is a single chip wireless solution.
9. A method of operating a receiver comprising:
operating in a first mode of operation when buffer conditions are not met; and
switching to a second mode of operation when buffer conditions are met,
wherein in the first mode of operation, the receiver receives and acknowledges frames in accordance with a radio protocol, and
wherein in the second mode of operation, the receiver mimics degraded radio conditions for at least a subset of frames received to induce a rate adaptation mechanism at the transmitting station;
wherein mimicking degraded radio conditions comprises:
stopping acknowledging of at least a subset of the frames received at one or more data rates by applying a mask to a list of accepted data rates to remove the one or more data rates from the list for frames which exceed a predetermined size, the mask defining at least one of a set of rates to be excluded from the list of accepted data rates or a set of rates which are to be included within the list of accepted data rates, wherein the mask is applied for frames exceeding a threshold size; and
dropping the frames exceeding the threshold size according to the masked list of accepted data rates,
wherein in the first mode, frames received at any of a set of accepted data rates are acknowledged according to the radio protocol, and in the second mode, one or more data rates are removed from the set of accepted data rates to create a revised set of accepted data rates and frames received at any of the revised set of accepted data rates are acknowledged according to the radio protocol, and
the revised set of accepted data rates comprises a data rate at which beacons are transmitted and does not include any mandatory data rates which exceed the data rate at which beacons are transmitted.
10. A method according to claim 9 , wherein the radio protocol is Wi-Fi.
11. A method according to claim 9 , wherein the buffer conditions are defined in terms of one or more of: input data rate, output data rate, frame size and available space in the buffer.
12. A method according to claim 11 , wherein the buffer conditions comprise a condition that a frame received exceeds a threshold frame size.
13. A method of operating a wireless receiver comprising:
receiving frames from a wireless transmitting station; and
when buffer overflow conditions are met, mimicking degraded radio conditions for at least a subset of the frames received to induce a rate adaptation mechanism at the transmitting station;
wherein mimicking degraded radio conditions comprises:
stopping acknowledging of at least a subset of the frames received at one or more data rates by applying a mask to a list of accepted data rates to remove the one or more data rates from the list, the mask defining one of: a set of rates to be excluded from the list of accepted data rates and a set of rates which are to be included within the list of accepted data rates, wherein the mask is applied for frames exceeding a threshold size; and
dropping the frames exceeding the threshold size according to the masked list of accepted data rates, and the method further comprising:
when buffer overflow conditions are subsequently not met, gradually returning to normal operation by gradually increasing the list of accepted data rates until the list includes all supported rates.
14. A method of operating a wireless receiver comprising:
receiving frames from a wireless transmitting station; and
when buffer overflow conditions are met, mimicking degraded radio conditions for at least a subset of the frames received to induce a rate adaptation mechanism at their transmitting station;
wherein mimicking degraded radio conditions comprises:
stopping acknowledging of at least a subset of the frames received at one or more data rates by applying a mask to a list of accepted data rates to remove the one or more data rates from the list, the mask defining one of: a set of rates to be excluded from the list of accepted data rates and a set of rates which are to be included within the list of accepted data rates, wherein the mask is applied for frames exceeding a threshold size; and
dropping the frames exceeding the threshold size according to the masked list of accepted data rates, and the method further comprising:
when buffer overflow conditions are met, entering a power save mode; and
subsequently, when no frames are received from a wireless transmitting station, exiting the power save mode and stopping mimicking degraded radio conditions.