659 research outputs found
Green Communication via Power-optimized HARQ Protocols
Recently, efficient use of energy has become an essential research topic for
green communication. This paper studies the effect of optimal power controllers
on the performance of delay-sensitive communication setups utilizing hybrid
automatic repeat request (HARQ). The results are obtained for repetition time
diversity (RTD) and incremental redundancy (INR) HARQ protocols. In all cases,
the optimal power allocation, minimizing the outage-limited average
transmission power, is obtained under both continuous and bursting
communication models. Also, we investigate the system throughput in different
conditions. The results indicate that the power efficiency is increased
substantially, if adaptive power allocation is utilized. For instance, assume
Rayleigh-fading channel, a maximum of two (re)transmission rounds with rates
nats-per-channel-use and an outage probability constraint
. Then, compared to uniform power allocation, optimal power
allocation in RTD reduces the average power by 9 and 11 dB in the bursting and
continuous communication models, respectively. In INR, these values are
obtained to be 8 and 9 dB, respectively.Comment: Accepted for publication on IEEE Transactions on Vehicular Technolog
Effective Delay Control in Online Network Coding
Motivated by streaming applications with stringent delay constraints, we
consider the design of online network coding algorithms with timely delivery
guarantees. Assuming that the sender is providing the same data to multiple
receivers over independent packet erasure channels, we focus on the case of
perfect feedback and heterogeneous erasure probabilities. Based on a general
analytical framework for evaluating the decoding delay, we show that existing
ARQ schemes fail to ensure that receivers with weak channels are able to
recover from packet losses within reasonable time. To overcome this problem, we
re-define the encoding rules in order to break the chains of linear
combinations that cannot be decoded after one of the packets is lost. Our
results show that sending uncoded packets at key times ensures that all the
receivers are able to meet specific delay requirements with very high
probability.Comment: 9 pages, IEEE Infocom 200
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
A Comparison of Selected GBN ARQ Schemes for Variable-Error-Rate Channel Using QAM
In non-stationary channels, error rates vary considerably. The paper compares Yao's Adaptive Go-back-N (GBN) Automatic-Repeat-Request (ARQ) scheme with Adaptive go-back-N with sliding window mechanism which both estimate the channel state in a simple manner, and adaptively switch their operation mode. The throughput of these schemes is compared in conditions of Additive White Gauss Noise (AWGN) channel with independent errors using 16-QAM modulation
On the Performance of the Relay-ARQ Networks
This paper investigates the performance of relay networks in the presence of
hybrid automatic repeat request (ARQ) feedback and adaptive power allocation.
The throughput and the outage probability of different hybrid ARQ protocols are
studied for independent and spatially-correlated fading channels. The results
are obtained for the cases where there is a sum power constraint on the source
and the relay or when each of the source and the relay are power-limited
individually. With adaptive power allocation, the results demonstrate the
efficiency of relay-ARQ techniques in different conditions.Comment: Accepted for publication in IEEE Trans. Veh. Technol. 201
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