1 / 10

Synchronization Requirements and Solutions for 802.11n

Synchronization Requirements and Solutions for 802.11n. Morgan H. Miki, John M. Kowalski Sharp. Problem:. Consumer electronic devices figure prominently in 802.11n usage models. CE devices however, require tight synchronization to maintain high quality audio if multicasting is done.

zelig
Download Presentation

Synchronization Requirements and Solutions for 802.11n

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SynchronizationRequirements and Solutions for 802.11n Morgan H. Miki, John M. Kowalski Sharp Morgan H. Miki, John M. Kowalski, Sharp

  2. Problem: • Consumer electronic devices figure prominently in 802.11n usage models. • CE devices however, require tight synchronization to maintain high quality audio if multicasting is done. • This presentation presents some results on the state of the art for synchronization in 11a, and recommendations to improve it for 802.11n. • Without some solution in this regard, the user experience of CE over 802.11n may be compromised. Morgan H. Miki, John M. Kowalski

  3. Clock difference jitter Packet detection jitter Channel jitter Clock difference jitter: Depends on clock precision and how often TSs are distributed Channel jitter: Depends on the movement of stations (1ns jitter for 30cm) 3 3 2 1 1 2 Packet detection jitter: Depends on synchronization algorithm, PHY rate and PER Clock Synchronization Tx clock: 20MHz ± 20ppm Rx clock: 20MHz ± 20ppm TS: Time Stamp TSF: Timing synchronization function TSF timer TSF timer TS TS Channel RX TX Clock synchronization is affected by Morgan H. Miki, John M. Kowalski

  4. Clock Synchronization requirements Desired for stereo audio (professional level) [1] Acceptable for one receiver Acceptable for stereo audio[1] Synchronization jitter 10ms 1ms 100us 10us 1us 100ns 10ns 1ns 100ps MPEG2: 500ns 802.11a 1394: app 40ns Why improve 802.11 synchronization? • HDTV/STDV/audio streams are 802.11n applications. • The jitter generated by wireless link should be reduced at wireless level, to minimize overall delay. • The effect is to make CSMA/CA behave more truly like a discrete time system. • Technology has improved anyway since 11a was introduced. Morgan H. Miki, John M. Kowalski

  5. Possible solution: • Add 8 byte 10ns unit Time Stamp in every QoS packet (Option) • Example of implementation may use DLL (Delay locked loop) eP eQ ef TX TSF Timer TimeStamp + PHY/MAC processing time 1 / T KP eI KI 1 fRX Z-1 fTX Loop Filter RX TSF Timer rf Tx/Rx timer synchronization error jitter PHY/MAC processing time is the time between packet detection and MAC to output the Time Stamp for DLL Morgan H. Miki, John M. Kowalski

  6. Simulation conditions • Tx and Rx clock precision: 20 ppm • Packet detection with legacy 11a preambles and PLCP. • App. 10% PER @ 16QAM ¾ coding rate. This results in packet detection jitter of ±100ns. (video applications) • Simulations with Channel B/D/E • Channel jitter considered as 0ns i.e. no station mobility (1ns jitter/30cm). • Interval between packets: 500us (max 30ms at high error rate region) Morgan H. Miki, John M. Kowalski

  7. Simulation results (channel B) Synchronization error jitter (ns) Jitter: < ±25ns Convergence time: 40s Time(s) Similar results for channel D/E Morgan H. Miki, John M. Kowalski

  8. Comparison Morgan H. Miki, John M. Kowalski

  9. Conclusions • The use of 8 byte 10ns unit time stamp in all QoS packets should be considered as option. • A great improvement from legacy 802.11 (10us to 25ns) can be achieved. • Synchronization can be further improved to acceptable stereo audio level by using higher precision oscillators (10ns) • Presently investigating the effects of synchronization when MIMO preambles, other information, other preamble formats, etc. are used. Morgan H. Miki, John M. Kowalski

  10. References • [1] Julian Dunn: “Sample clock jitter and real-time audio over the IEEE1394 high performance serial bus”, Nanophon Limited Morgan H. Miki, John M. Kowalski

More Related