30,263 research outputs found
Using Channel Output Feedback to Increase Throughput in Hybrid-ARQ
Hybrid-ARQ protocols have become common in many packet transmission systems
due to their incorporation in various standards. Hybrid-ARQ combines the normal
automatic repeat request (ARQ) method with error correction codes to increase
reliability and throughput. In this paper, we look at improving upon this
performance using feedback information from the receiver, in particular, using
a powerful forward error correction (FEC) code in conjunction with a proposed
linear feedback code for the Rayleigh block fading channels. The new hybrid-ARQ
scheme is initially developed for full received packet feedback in a
point-to-point link. It is then extended to various different multiple-antenna
scenarios (MISO/MIMO) with varying amounts of packet feedback information.
Simulations illustrate gains in throughput.Comment: 30 page
Optimal Control of a Single Queue with Retransmissions: Delay-Dropping Tradeoffs
A single queue incorporating a retransmission protocol is investigated,
assuming that the sequence of per effort success probabilities in the Automatic
Retransmission reQuest (ARQ) chain is a priori defined and no channel state
information at the transmitter is available. A Markov Decision Problem with an
average cost criterion is formulated where the possible actions are to either
continue the retransmission process of an erroneous packet at the next time
slot or to drop the packet and move on to the next packet awaiting for
transmission. The cost per slot is a linear combination of the current queue
length and a penalty term in case dropping is chosen as action. The
investigation seeks policies that provide the best possible average packet
delay-dropping trade-off for Quality of Service guarantees. An optimal
deterministic stationary policy is shown to exist, several structural
properties of which are obtained. Based on that, a class of suboptimal
-policies is introduced. These suggest that it is almost optimal to use a
K-truncated ARQ protocol as long as the queue length is lower than L, else send
all packets in one shot. The work concludes with an evaluation of the optimal
delay-dropping tradeoff using dynamic programming and a comparison between the
optimal and suboptimal policies.Comment: 29 pages, 8 figures, submitted to IEEE Transactions on Wireless
Communication
Rtp and the datagram congestion control protocol
We describe how the new Datagram Congestion Control Protocol (DCCP) can be used as a bearer for the Real-time Transport Protocol (RTP) to provide a congestion controlled basis for networked multimedia applications. This is a step towards deployment of congestion control for such applications, necessary to ensure the future stability of the best-effort network if high-bandwidth streaming and IPTV services are to be deployed outside of closed QoS-managed networks
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