Poll scheduling for periodic uplink and downlink traffic
View Patent ↗An apparatus and method for polling stations that transmit and receive periodic traffic streams are disclosed. The illustrative embodiment determines when to transmit a frame comprising a data payload and a poll to a station based on (i) the temporal period and temporal offset of the traffic stream transmitted by the station, and (ii) the temporal period and temporal offset of the traffic stream received by the station, such that delays for either the transmitted traffic stream or the received traffic stream are reduced. The present invention is particularly advantageous for latency-sensitive applications such as voice and video telecommunications.
1. A method comprising:
(a) receiving
(i) a temporal period π,
(ii) a first temporal offset φ 1 for a first stream of frames queued for transmission by a first device in accordance with said temporal period π, and
(iii) a second temporal offset φ 2 for a second stream of frames that arrives at a second device in accordance with said temporal period π, wherein said second stream of frames is for forwarding to said first device; and
(b) determining a third temporal offset φ 3 based on at least one of φ 1 and φ 2 for a third stream of frames transmitted from said second device to said first device in accordance with said temporal period π, wherein each frame of said third stream comprises a poll and a payload of a respective frame of said second stream.
2. The method of claim 1 wherein said determining said third temporal offset φ 3 comprises selecting φ 3 from one of
(i) φ 1 −T, wherein T is a transmission delay for a frame transmitted from said second device to said first device; and
(ii) φ 2 +G, wherein G is a processing delay associated with generating a frame of said third stream based on a respective frame of said second stream.
3. The method of claim 2 wherein φ 1 −T is selected for said third temporal offset φ 3 when either one of
(i) 0≦(φ 1 −φ 2 )≦π/2, and
(ii) (φ 1 −φ 2 )≦−π/2;
and wherein φ 2 +G is selected for said third temporal offset φ 3 when either one of
(i) (φ 1 −φ 2 )>π/2, and
(ii) −π/2<(φ 1 −φ 2 )<0.
4. A method comprising:
(a) receiving
(i) a polling request from a device, wherein said polling request specifies a temporal period π and a first temporal offset φ 1 for a plurality of expected future transmissions, and
(ii) a first stream of frames from at least one of a plurality of other devices in accordance with said temporal period π and a second temporal offset φ 2 ;
(b) determining a third temporal offset φ 3 based on at least one of φ 1 and φ 2 ; and
(c) transmitting a second stream of frames to said device in accordance with said temporal period π and said third temporal offset φ 3 , wherein each frame of said second stream comprises a poll and a payload of a respective frame of said first stream.
5. The method of claim 4 wherein said determining said third temporal offset φ 3 comprises selecting φ 3 from one of:
(i) φ 1 −T, wherein T is a transmission delay for transmitting a frame to said device; and
(ii) φ 2 +G, wherein G is a processing delay associated with generating a frame of said second stream from a poll and a payload of a respective frame of said first stream.
6. The method of claim 5 wherein φ 1 −T is selected for said third temporal offset φ 3 when either one of:
(i) 0≦(φ 1 −φ 2 )≦π/2, and
(ii) (φ 1 −φ 2 )≦−π/2;
and wherein φ 2 +G is selected for said third temporal offset φ 3 when either one of:
(i) (φ 1 −φ 2 )>π/2, and
(ii) −π/2<(φ 1 −φ 2 )<0.
7. The method of claim 4 further comprising:
(d) receiving a frame from said device; and
(e) forwarding said frame to at least one of said plurality of other devices.
8. The method of claim 4 further comprising receiving at least one of:
(i) said temporal period π, and
(ii) said second temporal offset φ 2 .
9. The method of claim 4 wherein said receiving and said transmitting are via a shared-communications channel.
10. A method comprising:
(a) receiving a first frame of a first stream of frames at a time τ 1 , wherein said first stream of frames is queued for transmission in accordance with a first temporal period π 1 and a first temporal offset φ 1 ;
(b) determining the time τ 2 at which a second frame of a second stream of frames is queued for transmission, wherein said second stream of frames is queued for transmission by a device in accordance with a second temporal period π 2 and a second temporal offset φ 2 , and wherein π 2 >π 1 ; and
(c) transmitting a third frame comprising a poll and the payload of said first frame to said device at a time τ 3 ;
wherein τ 3 equals τ 2 minus a transmission delay T when τ 2 <(τ 1 +π 1 /2); and
wherein τ 3 equals τ 1 plus a processing delay G when τ 2 ≧(τ 1 +π 1 /2).
11. The method of claim 10 further comprising (d) receiving at least one of:
(i) said first temporal period π 1 ,
(i) said second temporal period π 2 ,
(iii) said first temporal offset φ 1 , and
(iv) said second temporal offset φ 2 .
12. The method of claim 10 wherein said receiving and said transmitting are via a shared-communications channel.
13. A method comprising:
(a) determining the time τ 1 at which the next frame F 1 of a first stream of frames will be queued for transmission by a device in accordance with a first temporal period π 1 and a first temporal offset φ 1 ;
(b) determining the time τ 2 at which the next frame F 2 of a second stream of frames will be received, wherein said second stream of frames is queued for transmission in accordance with a second temporal period π 2 and a second temporal offset φ 2 , and wherein π 2 >π 1 ; and
(c) transmitting a frame F 3 comprising a poll to said device at a time τ 3 ;
wherein τ 3 equals τ 1 minus a transmission delay T when τ 2 ≧(τ 1 +π 1 /2); and wherein
(i) τ 3 equals τ 2 plus a processing delay G, and
(ii) frame F 3 also comprises the payload of frame F 2 when τ 2 <(τ 1 +π 1 /2).
14. The method of claim 13 further comprising receiving at least one of:
(i) said first temporal period π 1 ,
(i) said second temporal period π 2 ,
(iii) said first temporal offset φ 1 , and
(iv) said second temporal offset φ 2 .
15. The method of claim 13 wherein said transmitting is via a shared-communications channel.
16. An apparatus comprising:
(a) a receiver for receiving:
(i) a polling request from a device, wherein said polling request specifies a temporal period π and a first temporal offset φ 1 for a plurality of expected future transmissions, and
(ii) a first stream of frames from at least one of a plurality of other devices in accordance with said temporal period π and a second temporal offset φ 2 ;
(b) a processor for determining a third temporal offset φ 3 based on at least one of φ 1 and φ 2 ; and
(c) a transmitter for transmitting a second stream of frames to said device in accordance with said temporal period π and said third temporal offset φ 3 , wherein each frame of said second stream comprises a poll and a payload of a respective frame of said first stream.
17. The apparatus of claim 16 wherein said determining said third temporal offset φ 3 comprises selecting φ 3 from one of:
(i) φ 1 −T, wherein T is a transmission delay for transmitting a frame to said device; and
(ii)φ 2 +G, wherein G is a processing delay associated with generating a frame of said second stream from a poll and a payload of a respective frame of said first stream.
18. The apparatus of claim 17 wherein φ 1 −T is selected for said third temporal offset φ 3 when either one of:
(i) 0≦(φ 1 −φ 2 )≦π/2, and
(ii) (φ 1 −φ 2 )≦−π/2;
and wherein φ 2 +G is selected for said third temporal offset φ 3 when either one of:
(i) (φ 1 −φ 2 )>π/2, and
(ii) −π/2<(φ 1 −φ 2 )<0.
19. The apparatus of claim 16 wherein said transmitter is also for forwarding at least one of said first stream of frames to at least one of said plurality of other devices.
20. The apparatus of claim 16 wherein said receiver is also for receiving at least one of:
(i) said temporal period π,
(ii) said first temporal offset φ 1 , and
(iii) said second temporal offset φ 2 .