896 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
Hybrid Automatic Repeat Request for Downlink Rate-Splitting Multiple Access
This work investigates the design of Hybrid Automatic Repeat Request (HARQ)
strategies for downlink Rate-Splitting Multiple Access (RSMA). The existence of
private and common stream as well as their conditioning for Successive
Interference Cancellation (SIC), gives rise to an expanded set of opportunities
for retransmission of failed packets. Specifically, we devise a scheme in which
the retransmissions are scheduled through the common stream, which offers a
higher success probability. With this, the common stream needs to carry both
new and retransmitted bits, which leads to a layered HARQ (L-HARQ) strategy
which is capable of trading off throughput and reliability. Simulation results
demonstrate that the devised HARQ scheme outperforms RSMA with conventional
HARQ, where each retransmission is handled independently through its own
stream. It also helps in closing the throughput gap between HARQ and Adaptive
Modulation and Coding (AMC) in the high Signal-to-Noise Ratio (SNR) regime
while also achieving a decreased Packet Error Rate (PER) and a lower latency
An Energy Efficient Semi-static Power Control and Link Adaptation Scheme in UMTS HSDPA
High speed downlink packet access (HSDPA) has been successfully applied in
commercial systems and improves user experience significantly. However, it
incurs substantial energy consumption. In this paper, we address this issue by
proposing a novel energy efficient semi-static power control and link
adaptation scheme in HSDPA. Through estimating the EE under different
modulation and coding schemes (MCSs) and corresponding transmit power, the
proposed scheme can determine the most energy efficient MCS level and transmit
power at the Node B. And then the Node B configure the optimal MCS level and
transmit power. In order to decrease the signaling overhead caused by the
configuration, a dual trigger mechanism is employed. After that, we extend the
proposed scheme to the multiple input multiple output (MIMO) scenarios.
Simulation results confirm the significant EE improvement of our proposed
scheme. Finally, we give a discussion on the potential EE gain and challenge of
the energy efficient mode switching between single input multiple output (SIMO)
and MIMO configuration in HSDPA.Comment: 9 pages, 11 figures, accepted in EURASIP Journal on Wireless
Communications and Networking, special issue on Green Radi
On an HARQ-based Coordinated Multi-point Network using Dynamic Point Selection
This paper investigates the performance of coordinated multi-point (CoMP) networks in the presence of hybrid automatic repeat request (HARQ) feedback. With an information theoretic point of view, the throughput and the outage probability of different HARQ protocols are studied for slow-fading channels. The results are compared with the ones obtained in the presence of repetition codes and basic HARQ, or when there is no channel state information available at the base stations. The analytical and numerical results demonstrate the efficiency of the CoMP-HARQ techniques in different conditions
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
Cooperative retransmission protocols in fading channels : issues, solutions and applications
Future wireless systems are expected to extensively rely on cooperation between terminals, mimicking MIMO scenarios when terminal dimensions limit implementation of multiple antenna technology. On this line, cooperative retransmission protocols are considered as particularly promising technology due to their opportunistic and flexible exploitation of both spatial and time diversity. In this dissertation, some of the major issues that hinder the practical implementation of this technology are identified and pertaining solutions are proposed and analyzed. Potentials of cooperative and cooperative retransmission protocols for a practical implementation of dynamic spectrum access paradigm are also recognized and investigated. Detailed contributions follow.
While conventionally regarded as energy efficient communications paradigms, both cooperative and retransmission concepts increase circuitry energy and may lead to energy overconsumption as in, e.g., sensor networks. In this context, advantages of cooperative retransmission protocols are reexamined in this dissertation and their limitation for short transmission ranges observed. An optimization effort is provided for extending an energy- efficient applicability of these protocols.
Underlying assumption of altruistic relaying has always been a major stumbling block for implementation of cooperative technologies. In this dissertation, provision is made to alleviate this assumption and opportunistic mechanisms are designed that incentivize relaying via a spectrum leasing approach. Mechanisms are provided for both cooperative and cooperative retransmission protocols, obtaining a meaningful upsurge of spectral efficiency for all involved nodes (source-destination link and the relays).
It is further recognized in this dissertation that the proposed relaying-incentivizing schemes have an additional and certainly not less important application, that is in dynamic spectrum access for property-rights cognitive-radio implementation. Provided solutions avoid commons-model cognitive-radio strict sensing requirements and regulatory and taxonomy issues of a property-rights model
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