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Showing posts from March, 2012

RTP Packetization for H.264 NAL Units

H.264 Network Abstract Layer Header How to Broadcast Multimedia Contents? RFC3984 (RTP Payload Format for H.264 Video) defines 3 modes: 0 (single NAL unit mode), 1 (non-interleaved mode), and 2 (interleaved mode).  Mode 0 requires you either use UDP fragmentation or tell the encoder not to generate NALs larger than MTU-X. Mode 1 lets you do fragmentation. Details of how to set up a fragmentation unit packet can be found in the RFC. Basically the fragmentation information is on the front. Small NAL units, e.g. SPS and PPS packets, can be aggregated together using single-time aggregation packets (STAPs). Each packet requires normal RTP headers with incremented sequence numbers but the same timestamp. Though a mark on the last RTP packet of a frame is expected,  it is not guaranteed. Mode 2 lets you fragment, combine, and interleave the transmission order to change how a burst loss will affect a stream, among other things.

Evolving Random Access Channel for IoT: III Slotted ALOHA Models

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Access Channel Enhancements for 1x Rel. F One Eighth Rate Access Probes for Smart Terminals Evolving Random Access Channel for IoT: I Introduction Evolving Random Access Channel for IoT: IV Dumb Access Probes and Smart Access Probes It is well known that the access channel design of 3G cellular mobile network is based on ALOHA models . More specifically it is based on a single-channel single-hub slotted ALOHA plus open-loop power control.  Indeed, there are many possible variations of slotted ALOHA.  Considering access channel configuration, there are the cases with a single shared access channel and the cases with multiple access channels.  Considering network configuration, there are single hub models and multi-hub models. Though multi-channel slotted ALOHA models have been intensively studied in computer engineering domain, a ALOHA model with more than one participating hub and more than one access channel hasn't received enough attention so far. I guess one reason is the